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MICROCOPY RESOLUTION TEST CHART
MICROCOPY RESOLUTION TEST CHART
" NATIONAL BUREAU OfSTIoNOARDS-1963-A
NATIONAL .BUREAU Of STANDAROS-I963-A
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Technical Bulletin No. 870 • May 1944
The Brown Spot N eeclle Blight of Pine
Seedlings
1
By P,\ UL V. SIGGl>RS,2 (/·ssociaie pathologist, Division of Forest Pathology, Bureau
of Plant Jndusi1'y, Soils, lind Agricultu.ral Engineering, Agricultural Research
rtriminislraiion
CONTENTS
SllnlI118ry .. _ ... ~ __
~_.
"
Di.cussion of the problem ... .
Description of the disease................... .
.Macular phaso. ..... .•. . .......
..,
Subepidermal im'asion ofheulthy tissuo ...
Taxonomy and synonomy of the causal
organisrn .. __ ~ "' .. _______ .. _ ~ _..... _.... __ _
Conidial sta~o .................
.\sci~erous sta~e, ........ .
SpeCImens exammc<L. w_ _
....
.
IIost range and geographical distribution
Cultural studies .................... .
:Materials and methods.......... .
Sporo germination ...., ... .
Temperaturo relatIOns ...... .
.. '- Ivloisture relations. __
N
__ . "
."
; . Light relution!;........... .
.- Hydrogen·ion relations '"
f Growth._........ ...... ..
l.,,' 'r~mperntu.re relations ...
J.lght relatIOns....... .
~ructillcation._ ............ ,.
'rime relations ......... .
.~'
Light relations ....... ..
.~ Summary of cultural stllllies..
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Page
Page
1 Inoculation cxperiments .............. ..
17
3 Uissemillntioll of the pnthogen ...............
17
5
Disselllinntion of conidia as related to me·
5
tearological conditions .... _............ _
18 6
Hnin ___ ....................... _... ..
18 Wind ... _........................ _.. .
19
20
~
Disc~~~\ci~cr~~u~c::::::::::::::: :::::::::: 20
9 [nfi<lenco of the. disease on seedling growth
11
und sun-ivai of longleaf [line .............. ..
22
11
ElIect on the growth rato of stands...... .
24
12
Natural reproduction..__ • ___ ........
24
13
Plantations ........... __ ....... _.... ..
26
13
EfTect of defoliation on the a.crage annual
13
hcigllL g-rowth in yarious height cla~ses .
27
14
Obscn'ations 011 sun'ival of seedlings in
14
plantations................ _.. _____ .... .
27
14 Soil fertilization in relation to growth of
15
dwarfed pines ......................__ ......
29 15 gfIect of single fires on tho disease. _____• ____ _
30
16), ~'ungjcidal.controL .••--..-- ....---- __ .... __ •
33
N ursenes ....... __ .... __ •____ .._... __ •..•.
11
33 16
Pluntutions ............................. ..
33 16 The disease and forest management prnct.ices ..
34 16 Literature cited ......... __ .... _............. _
35 SUMMARY
::: Brown spot needle blight is one of the major obstacles to Iilcreased
(Pinus palustris lvril1.)-a forest
;resource thnt furnishes 40 percent of American-produced turpentine
~production of southern longleaf pine
Submitted for publication October 1943. 'l'he sub;ect mutter of this bulletin was submitted to the
.' faculty of the gruduatcschool of the UniYersity of Minnesota in partial fulfillment of the requirements for the
degree of doctor of philosophy. This Investi~ation was conducted in cooperatio:J with the Southern
Forest and Range Experiment Station, }'orest <iervice, United States Department of Agriculture.
'The author wishes to express his thanks to Carl Hartley, of the Division of For~.st Pathology, under whose
direction the work was done; to E. C. Stakman, of the UniYersity of Minnesota, and to A. F. Verrall, of the
Division of Forest Pathology, for their advil'e, assistance, und cooperation; to Hoy A. Chapman, of tho
Forest Service, for help in statistical analysis and in thn preparation of the height'growth curyes; to Howard
N. Lamb, form~rlr. of the Division of Fornst Pathology, Clyde M. Christensen, of the UniYefsity of Minne·
sota, A. F. Verral , Franklin G. Liming, of the Forest Service, and L. D. Glenn, formerly of tho Division
of Forest Pathology and of the Forest Sen-ice, for assistance in the field work; to William W. Diehl and
John A. Stevenson, of thn Di\ision of Mycology and Disease Survey., of this Bureau, and to Louise Dosdall,
Clyde M. Christensen, and F. H. Kaufert. of the University of Minnesota, for assistanee in the taxonomic
study. The initial experimental plot.s were es~~blished on land then owned by the Great Southern Lum·
ber Co., Bogalusa, La., and tho writer Is indebted to J. K. Johnston, formerly forester for this company,
Bnd to his successor, Paul Garrison, of the Gnylord Container Corporntion, for many courtesies. Labor
from the Civilian Conservation Corps was used ill SOIllO of the fleld work.
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573337--44----1
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2
TEOHNICAL BULLETIN 870, U. S. DEPT. OF AGRICULTURE
and rosin, makes up It large proportion of the total annual cut of
southern yellow pine, and, b('causc of its long fiber, is well adapted
for paper pulp. This disease is caused by a fungus, Scirrhia acicola
(Deal'll.) Siggers, which defoliates seedlin~TS and delays the growth of
the trees. It has been estimated that 9,000,000 ncl'cSro( cut-ovcr'
longleaf pineland in the South is ba,rren of forest growth, most of it
nonagricultural laud that will remain ullpl'oduetive until artificially
mforested. Bringing this land into successful production and pei·­
petuating the longleaf forest type is thus an nndt'l'taking of con­
side,mble importance, and its success involves control of the brown
spot disease.
As a basis fm' -planning control measures foJ' these lJllJ'poses, the
United Stn,les Depa,l'tment of AgI'icu1tm'C' in 1929 IlC'gnn inv('stign,tions
to obtn,in infol'Hll1,tion on (1) thC' cfrN~t of tilt' diseast' on the dC'v('lop­
ment of longleaf pint' s{\cdlings in plantatiollS filld on stands of nntural
reproduction indep<'ndcntl}r of fir'('; (2) thc' influenc'c' of Sillgjp fires on
the diseuse; (:3) the efl'retoE factors of {'l,,"ironmcnt 01.1 thc' cliRensc proe­
css; (4) the tn,xonomie position of tiL(' pt'lthogcn; and (5) pl'l1etical
methods of disease' control.
These il~\ "stign,tions thus Involn:'c! a study of tIl(' ()r~:l1lisl1l that
en,uses hrowll spot disense. iL SUITPY of infectecl arens, a study of the
results of en.rliee iovestigntions, and experiments with possibh' {'ontrol
mensnres. The findings, whieh t),1'e of ('yell greater importanC't' J10W
than they would hn,vc been whell the work \\'lLS undcl'takpll, mn,y be
summarized as follows:
Econol/de import,mlce oj blight.-Hcrorcstntioll ill the South has long been compli­
cated by thc prcsence of a destructive leaf di~('age of seedlings of longleaf pine, eom­
IDonly known as brown spot.
Extcnt oj illJection.-Brown spot disease has been found in the Uni1;ed Rtates on
24 species 01' varieties o[ pincs, of which i.0 Me native to the RO\ltlwa!'t and 14 occm:
as exotic!' hI the EaRt. It occurs in all coaf<1':tl i4taieR [rom ::\ort.h Carolina to Texas
and ilJlancl in Arkansas, T(,Ill1(:~ssee, and Ohio, and ther(' is a single COllection from
Oregon on Pimls al/enmlia Lemm.
'l'a.To1101ll?! oj Ihe paLlwocn.-I,ong-stanclinf{ eOnfllf<ion ill th!' tnxonolllicliterntilre
of thc' browlI ~po! fungus ha::; been due (;0 til(' inclu~ioll of f;('\'ernl fungi af:Bociated
with 1~"iflllR S(}lllewJw.t; similm' to tho~(' of the trlle I))'(nnl "pot. 'I'll!' illl[J!'l'fect
stage of th(~ fUl'gliS is l'eferrCl'! to Le(,ollo~tic[1L acieo/a (Thi'!m.) By,d., the perfect
stage to ,C:l'irrhia acicola (])(olll'n.) fiigu;ers.
Sport,!, viability and enviroIl11lcnt.-The cfrcct of somc factors of the clI\'iron~ne,nt
on the f!;crlllillatioll, growth. IWc\ fl'tlet.ificatio!l of thc olwwili/ll 1\"(1S I'tlidiC'd in the
laboratory. Dr,l' laboratory ,,{Ol'age :td\'erl'cly afl'pc[('(l tll<' \"iallilit~y of "pores
from fruit lJOdi(''; on needles. A "tick,I' matrix ill which tIl(' (''1[1idill Inlre produced
preventNI di~pers:tlof th('~(' ~p()r('s hy ail' (,llrrentR. The llJll){':" t IU'l'lllallimit, for
germination was :\,pproxill1atcly 3i)0 ('.: tIl(' l(l\\'cr lay bei,\\'et'll ij" and 1.00. The
minimum and Jllaximum temp!'r1itllr{'l-1 fol' I-(I'o\\"th appeal' to he l'lightly b('lo,," 5°
ane! at. 35°, l'('s]lC'C'tive)y, and thC' opt.imuJll slightl~' niJol'e 2.)". The alkaline
limit for germination lay bN.\I·C'ell 1111 fl.3 and s.n: the acid limit', helow pH 4.3.
The average diame{('l' of nine conidial if'oJaieil nftPl' 2-wccks' gro\\'th on potato
dextrose agar at 2ii o C. waf; 2.65 1111ll., which approximates the ::;i7.c of sillgle macu­
lar lesions on needles of P. 1J(llllstds Mill. '\'iablc conidia developed in monospo­
rous cultures in a minimum of 14 cla\'~.
lIfethods oj JunOlls (H.~scTl!in(/tion.~A study of the dissemination of brown spot
disease confirmed earlicr work indicating that conidia of the pathogen ar(' di~sem­
inated locally by the splashing of rnin;on the other hand, th!' ascospores of the
brown spot fungus arc di~persed to a larp;c extcnt. by ail' currents. Thi:; inoculum
is formed on longleaf pine only after death of most of the needle, and it if> the caWle
of a general but low-degree infection that lIsUltlly appears in springtime on the
foliage of seedlings shortly after a winter fire. Dissemination of coniclia and asco­
spores appears sharply limited to tJlCagencies of rain and wind, respectively. Di$­
ease escaJ;>e, as a result of freedom from serious defoliations apparently due to the
sporadic occurrence of ascosporic inoculum and limitation of conidial.iniection to
BROWN SPOT NEEDLE BLIGHT OF PINE SEEDLIlWS
3
rain-splash distances, is thought to account for early active height growth in sev­
erallongleaf pine stands.
Defoliation clfetts.-Tlw dwarfing effect of brown spot disease on the early
rate of growth of stands of longleaf pine seedlings was studied under natural
couditions by controlling the disease with fungicides over a period of years. A
measure of the cumulative effect of the defoliations on height growth was obtained
by comparing the subsequcnt growth of sprayed seedlings with that of untreated
and diseascd sE'edlings in adjacent plantation rows. In \Vashington Parish, La.,
the height I'rowth of one stand has aheady been clelayeclmore than 10 years. In
a second plantation, the lwerage height of the sprayed seedlings at the end of their
eighth season in the field was 11 feet 2 inches, whereas that of the diseased seed­
lings was 1 foo~ 1 inch. In central Louisiana, the average height of a lot of seed­
lings that were treated five timeR in <1 years was more than double that of the
nonsprayed seedli!.1/!:s in the same 4-year-old plantation. Complete defoliation as
a seasonal pathological process rc!ardecl the annual height growth in the next sea­
son to one-seventh or less of that of sprayed healthy s('('cllings in adjacent rows.
For a constant percentagE' of the dif'eai;e, the effect of partial defoliation was to
cause proportionat('ly mOT(, dwarfing of the smaller ;;C'edling:.' than of the larger.
'1'he dptrimental effect of severe attacks of the riisC'fLsC' on surd val of planted seed­
lings was indicatE'd b~' greater mortuliLy all1011g unsprayed lots of seedlings in
tll(' oldC'r demonstmlional at·C'IlS.
Surl.'it'lli (I,.ffecled by ciffolial-ion.-At le·.l~t three ~uc(,E'~"ive annual defoliation~
wer(' rcquirNI to weak('n u· ficcdling ~ufTiP(ent1y to raw;(' death. Death of seedlings
as a rC'sult of gradual wqnkenillg by prematurc defoliation is an attrition process
that ma~' go on unnoticed for years. The longer a seedling ~tand remains dwarfed
by the disea.'<e the greatC'r the hazard thal. the iitalld will u(' depleted by other
adversC' facl'or~ of the environment. By delayin.l! mpid height growth for a decade
or longer, brown ,>pot needle blight contributes indirectly to low survival, though
other factors ma~' be th(' direct cause of death.
Soil-improvement stlulies.-The growth capacity of stunted, diseased ~ongleaf
pines can be altered by improving the chemical composition of the soil. In a dense
stand of this typc, h('tL\'Y tLpplicatiolls of a 3-10-3 fertilizer induced rapid growth
in height among !'C'\'cral seC'dlings in a field te::t plot. After fertilization, the quan­
tity of uninfcctec1 foliage gradually illcr('asecl. Evrntually, as the capacity of the
seedlings to elaborate rC'servC' food impro\'ecl, the desirable type of heigbt growth
followC'd.
Effect of firps.-SinglC' fir('s during the dormant season gr('atly l"C'duced the dis­
etUw durin!!; the firM growing seal'on thcr('llfter and to a les::er cxtC'nt during the
second. 'I'hi' C'XU'lIt of thif' rpclu("(iol1 and the ~('ai<onal duration of the sanitary
eff('ct depend mtlinly on thC' ;;ize of the tHC'a burned, tho inlensily of the fire, the
qUlLlItity of infective mUIPrial nrtillg a~ an C'xternal ~Ollrce of available inoculum,
and on I'C'a;<onnlll1('tporological coudit i()n~.
Control IlIrtlwtls ("ollll}(lr('ll.--~]lr:tyillg and·soi! 1l111(,llc1mrnt:=:. eX('f'pt under nurs­
ery conditkns, do not appNll" eC·OIlOrnieally ff'a~iillC' for controlling brown spot dis­
easp ''':''Jh~ 111 inim lim 1'1~ra.~· t rpat nwnt neprlt'cl to in~ure a :::ati~factory sapling stand
-two s('mia.nllllul ~pmyjn~" applipc[ durin!! each of tlw fir~t two H'aSOIlS in the
fiC'ld--\\ould irIC'rpas(' OJ(' eo,t of n. plantatioll at ll'a;;t S-l an ncrC'. ('Olltrol of the
disc'n,,(' by TlC'rio<iir 11':<' of fin', 11>' originally r('(·'JIl1nH'lHk'l by Chapml111, appC'ars to
he t.lw l"H[ionull)!'Ocedll.rt> whf'l'f' fJw (li;;i'a~l' i" ,~('riolls on rpprndllclioll areaE'. In
general, tlw <'unitary p(]"pc:! of II giv(~n fl.r!' will vary dirC'ctly with its size and in­
vcrsC'ly wilh tlll' quan! il~· of Willd-hlowlI ino(!ulul1I. Thl' r(,~l1lt:; of thi:; in\'estiga­
tion, whcll cnrrl'lilted with t1 I'llleV of tltC' tl'chniqup of cont['ollc'c[ burning, will
, furnish the> 1Jn.~i~ for tll<' 11~P of fire illloll~l('tlf pitH' l'('l.!;(' llC'rfit ion.
DISCUSSION OF THE PROBLE:M
Two main plmses of the impoTlllllt sijyicultul"ul problem in the
South concerned with the tc'[orestn,lion or cul-over longletlf pillclands
are: (1) l~('gencration of ]onglraf pille (Pinus ])alusil'i8) on lanclmore
or 1,' ..> adeq nately stocked with seed trees of tht' same species, and
(2) l.rtificiuJ l"eforestn,lion of extensin' ureas, bmTt'1l of forest trees of
economic importance.
Accorclingto Demmon (8),3 9,000,000 [lcres of this cut-oyer longleaf
pineland is barren of forest regrowth. As this land is nonagricultural,
most of it will remain in its present nnproduetive condition until
'Italic numbers in parentheses rerer to Literature Cited. o. ~Ii.
4
TECHNICAL BULLETIN 870, U. S. DEPT. OF AGRICULTURE
artificially reforested. As longleaf pine furnishes 40 percent of
American-prod:uceJ turpentine and rosin, makes up a large proportion
of the total annual cut of southern yellow pine, and is well adapted for
paper pulp, bringing this land back into production and perpetuating
the longleaf forest type become undertakings of considerable im­
portance.
The reduction in the commercial range of longleaf pine 11as been
followed by reforestation by P. taecla L. and P. caTibaea Morel. of
extensive areas that it once occupied. Some causes of this change in
ecologic type arc understood. vYahlenberg (38) lists a number of
factors that place longleaf at a disadvantage in competition with
associated species of pines.
Although the growth habits of longleaf pine Ill'(\' known, as indi­
cated by Forbes (12), Pessin (21) vYahlenberg at aI. (39), and Wakeley
(40), satisfactory regeneration of the species by artificial and by
natuI'al means is, OIl the whole, lULzardous and uncertain. "While
attempts have been made to bring extensive areas of denuded longleaf
pineland into productiv~ use by planting P. caTibaea and, to a lesser
extent, P. taeda, neither of these species has as ;vet demonstrated the
same capacity as P. pal'llstTis to produce a crop of timbcr on true
longleaf sites.
The en,rly growth hlLLit of 10ngleILf pine is unusual and unlike that
of other southern pines. rrhe seedlings, cYcn on optinUlm sites, do
not start vigorous height growth until they IU1YC passed through a
preliminary period of root and foliar development. vVahlenberg
(38) luts pointed out one definite character of the species-that
active and vigorous height growth does not start until the din,meter of
a seedling, regardless of age, 1uts become at least 1 inch at the ground
line. It is apparent that any condition 01' factor that keeps seedlings
from reaching the minimum diameter for active height growth is
important. Also it is cOIlut:ivable that the efl'ect of such factors
might be so balanced against the growth capacity of the seedling that
it would remain perennially stunted.
One of these factors, long suspected of importance in the regenera­
tion of longleaf pine, is the needle disease, commonly known as brown
spot (17), caused by SciTrhia acicola (29). Chapman (3), one of the
first to recognize the economic importance of the disease, which was
then ascribed to Septona pini, recognized that competing vegetation
and the needle disease were important factors in natural regeneration
and recommended periodic controlled burning of stands of natural
rephiduction as a sanitary mensure for disease control and to reduce
the competition fTOm vegetative cover. His recommendation was
made possible by the remarkable resistance to nre damage possessed
by longleaf pine seedlings after they are a year old and before they
start vigorous height growth. The discussion in American forestry
circles) following publication of Chapman's paper, o:eated a strong
interest in the Use of fire for the perpetuation of the longleaf pine type.
In 1928 the Southern For()st and Range Experiment Station, in
cooperation with the Division of Forest Pathology, initiated pre­
liminary spraying of seedlings in plots laid out in dense natural long­
leaf pine reproduction. This activity was undertaken not as a
practical measure of disease control but as a means of gaging the
dwarfing effect on seedling development of the defoliation caused by
the fung~s.
BROWN SPOT NEEDLE BLIGHT OF PINE SEEDLINGS
5
DESCRIPTION OF THE DISEASE
'MACULAR PHA.SE
The following detailed account of the various manifestations of
brown spot diseDse is based largely on collections of infected foliage of
longleaf pine from various sources, from which it was found that the
pathogen causes two types of definitely marginate macular lesions.
The commoner typc of lesion is first straw yellow and later changes
to a light brown. A chestnut-brown discoloration darker than
the rest of the lesion often borders the spot and shows up about the
time the fruiting bodies form. Spots with dark-purplish borders are
common after the advcnt of cool weather in the fall. Single infec­
tions give rise to circular lesions, but contiguous lesions, apparently
originating from two or more simultiUleous infections, frequently
coalesce to form irregularly oblong areas. Single-spore infections
may girdle the needle, depending somewhat on the age and size of
affected foliage. Premature death of the foliage is due to multiple
spot infections, not to an isolated girdle. The length of the mature
spot is about one-eighth of an inch, a size corresponding almost to
the diameter of monospo ric colonies of the fungus when fruiting
begins.
'Yhen the blighted part of a needle dies, the areas of green tissue
betwecn the spots sm'ink morc than those occupied by the macular
lesions. Differential shrinkage of contiguous lesiona1 and non­
lesional parts of the same needlc gives an embossed appearance to
tl18 dead surface. Other diagnostic characters of the disease are
the brown color of the spots and their small sizc and sharp margins.
A sccond type of macular lesion has been aptly called "bar spot,"
and was first mentioned in the literature relating to the disease by
Verrall (36). He cxplained their origin as a host rcaction to the in­
fcction whereby the infiltration of resin into the mesophyli layer of
the necdle l'estrictednormul growth and reproduction of the pathogen.
V crrull also demonstratcd thn,t all gradations exist between the two
types of macular lcsions.
In the formation of the typical bar spots, the rcaction of the host
to fungus infection precedes allY outward manifestion of the pathogen
in the nccdle; that is, bar spots begin as plain amber-yellow 4 bands
encircling about one-eighth of an inc:1. ofthe needle. Later, that part
of the bar spot invaded by the fungus shows up more or less centrally
in the ycllo\v area. as a. circular brownish spot about the size of a pin­
head. The brow11ish, lesio11al part. of a bar spot seldom girdles the
leaf and is usually locfllizcd on one side of the needle.
Bar spots arc the prevalent type of brown spot lesion on the foliage
of large stLplings and mature trees, but they also occur on slllall seed­
lings. Apparently they may be formed at any season, provided the
plant is able to produce resin in sufficient quantity to restrict the
internal develoPlllcnt of the pathogcn. In plantations, however, ob­
servations indicate that bar spots first appen.r in the fall of the first
season in the field.
The two kinds of spots common on longleaf pine foliage have been
considered with refercnce to occurrcnce and dcvclopment on single
needles. In the scasonal development of the diseasc on sllsccptible
seedlings, conidia from pycnidiu on ovcrwintered foliage cause primary
I
Color accordill~ to Ridgway (!!).
6
TEOHNIOAL BULLETIN 870, U. S. DEPT. OF AGRICULTURE
infections at or near the tips of young elongating needles in April.
By :NIn.y, spores from fruiting bodies in priml1J'Y lesions hlwe caused
secondary spot infections between and below the primary spots. In
June, diebnck of the tips of all the older lH'edles on a seedling hns set
in. vVith the gl'udual de!1th of the upper 01" older parts of the needles,
the affected parts Clll'v'e outward fLnc1 down. By the latter p:trt of
the smmncr the inj 1I1'ious elred of tlH' slimmer phnsc of tl\(' diseuse
becomes evident. If the seedling is tall enoughfol' its needles to be
completely above the level of the grass and thus exposed to infection
on nIl sides, the foliug(' will have an ou te'l" zone of dend tissue sur­
!'olUlding a narrower spoLted zone of partly green [l;l)c\ pltrtly deud
tissue. The green inner zone oj' folinge is eompospd of young needles
und the basnl segments of older 011(,S.
SUllEPlDEHlIlAL INVASION 0)1 IfEA1:I:IIY TISSUE
"YIlCreas localized spotting ls the chlef mnnifestation of the dise~sc
in spring and SlIllUner, l1lueh needle tissue is llt111Ually killNl outright
after tho advent of cool weatherby subepidermal l1dnUlCC of tIte fun­
gus in green tissue below the ol(l spots (S6). This process llceounts
for the destrllction of marc needle tIssne than that eaused by spotting.
It occurs ut a maximulll rate bctwN'J1 the first of .March and the
middle of April. Small chlorotie H(~ckillg of the green pmts of the
needle, sometimes extending downward. seyerul inches, is the first
indication that the pathogen hns invaded the lllesophyll Inyel". The
affected needles yellow quickly and finally often nssume the orange­
red hue of needles killed by fire.
TAXONOMY AND SYNONOMY OF THE CAUSAL ORGAl\ISM
Ascigerous stage:
Sdrrhia acicola (Dearn.) Siggers. Phytopathology 29: 1076-1077. 1939.
Syn. Oligostroma acicola Dearn. l\[ycologia 18: 251. 1926.
Systremma acicola (Dearn.) ViTolf and Barbour. Phytopathology 31:. 61-74.
1941.
Conidial stage:
Lecanosticta acicola (Thum.) Syd. Ann. Mycol. 22: 400. 1924.5
Syn. Cryptosporium acicolmn Thum. Flora [.Tena] 61: 178. 1878.
Septoria acicola (Thum.) Saec. Sylloge Fungorum 3: 507. 1884.
Lecanosticta pini Sycl. Ann. Mycol. 20: 211. 1922.
CONIDIAL
ST•.W E
Considerable COIl fusion exists in the taxonomic literature of the brown spot
fungus, largely because of failure to distinguish bctween several fungi associated
with lesions somewhat similar to those of the true brown spot. Two or more
species of hyaline-spored pine needle fungi arc found in herbaria under names
applied to the color-spored brown spot fungus. The hyalinc-spored forms are
typically northern in distribution. 1'he brown spot [ungus, however, has been
collected north of the Ohio River and in southwestern Oregon, although more
commonly parasitic on pines in the South. An overlapping host range occurs in
the northern part of the Ohio Hivcr Valley. Althollgll a pronounced reddish cast
to the needles is typically associated with lesions npparcntly caused by the hyaline­
spored group, pigmentation of the lesions ill Some collections may be dcfinitely
brown. Even spore length is not always reliable ali a distinguishing character.
The only positive characters found that differentiate a group of hyaline-spored
fungi from the true brown spot fungus were stromatic structure and spore width
and color at maturity. In the following discussion, based on published descrip­
tionsand examination of herbarium material, ~ttempt has been made to remove
• In part, Actinothprium marginatum Sacco (Weir No. 10330) is not this fungus.
BROWN SPOT NEEDLE BLIGHT OF PINE SEEDLIXGS
7
long-standing c;onfusion in the taxouomic literature of the brown Rpot fungus
due to the mixing in herbaria of different fungi undcr the 'lame DUll"le.
The first collection of the brown spot fungus on record was made in 1876 by
H. W. Ravenel, at Aiken, S. C., on Pinus voriobilis Lamb. 6 In 1878 De Thiimen
(84, p. 1(8) publiilhed the following description of CryplOS]loriu11l odeol1l11l from
Ravenel's collection:
s. Cryplos].!Oriu1lI acical1l1li Thilm. nO\·. ~lW~.,
c. J)crithecils Jl~rvHlis. ~f('guriis, plus 1I1UIllSV(l linrnri rli~posius, [(Jetts. pwu'tiformibus, 5ubglohosis,
atris; spori' cylilldrids. (·un'3(C1·1unulotis. ulrinqu~ snbangustutis, rotundali~, Sillll'liCibus, llumcrosissimfs,
pallid~ (us~o'~ris~is, 2, nUll. lon~.. 3.5-·\ mm. trl4<S.
Cnrolinn austTlllis: Aiken in Pin; rarl,,~;/i. Lamb. (P. 1lIitis 1I1clH.) fuliit· aridis. (no.2O'2.)-Leg. II. W.
Ra.. cneJ.l
A specimen from De Thii mc'J) labeled "CrY]Jiospol"ill1J1 acicalum Thiim. nov. l'pec."
is in the mycological co\1(>ctiou~ of tlw Bureau of l'ltlnt Im\u;:try, Boils, and Agri­
cultural EUA'ineering, fit Belts\'ille, illd. (l'-lycothC'cu l'nh'C'rsalis 1484), OIl P.
voriabilis. Qaccardo (24, 11. 507) shifted the fungus to Septoria Fr. (14, p. 480,
1832; em. 23, 1). a, 18RO), 011 th(' basi!; of tIl<' spptntC' "pore!', naming the fungus
Septaria arim/a (Thiim.) Sncc. The description;: of the brown spot fungus given
by De Thtimen and br Haccardo are vClT similar. III 1887 George l\lartin (20)
reworded Snccartio's description, but used the name S. acericoia, apparently a
case of mis~pelling.
In 1920 Saccartio (2;;, p. 8m rl('~('rilwd Artilloth!lrilllll 1IlClrgina!1l1lt on P. pon­
derosa collected by Sl1:1ti uck I Weir Xo. 10380) at Orofino, Idaho. The writcr
found in his examination of thi", material two h~'nliup-sporcel fungi on the same
needlo, a Leplo.•iro/llll and anoUler fungus in rpc1dillh lesions with a fruit boely
somC'what similar in gross iltructu!"(· to oaccnrclo':, ,septaria odeola (Thiim.) Sacc,
(CryplosporiulII acicolulIl ThUm.). As Bydow (81) pointed out later, it appears
that Sncc:ardo'il description of A. IIw'rginalu /Il was based Oll the fruit body of a
species of Lrploslroma ancl thC' l:lpores of the otlwr fungus.
In 1922 Sydow (80, p. 211) describ£:'ci Lrcanosticta 1Jini from a collection by J. A.
Hughes on P. iocda ("-eir No. J29,lO), Pike City, Ark.s His generic description
follow~:
LCCU710$/ictn I'o)"lt no\·. gPn, ExcipulaC\'~rum,
Frucht~ehlius(' r-fnzpln olkr ZII weni~ell dicht ~ph:illftdn.JIl nwlIr oder weniger krnftig enl.\,.fckelten Basal­
stroma von prosenchYlllntisclw!Il meis( zi('mlich dunk.1 geW rhlelll (;rwebe fillfsitzend, bald hervorbrechend
und fast ~anz ol'l'rfifichliell ,wrd('nd, ~lIltt ml('r lim nandl' \"on sich pinsl·l.lrtig nufli:iscnden Hyphenenden
des Deillillsos lind Bas.11~tronllls A('wiIJlpen. sieh "'eit schiiss"iforlllig annend, ,'on knorpelfger, feueht zlih
gel11tinos-fleischi~cr Beschntfenlwit. Sporen 7slin(lrisch, oft stark geknimmt. ohne oder mit cinigen, meist
ziemlicl1 uodeutlicbcn Qu('rw.«nden, oliYenbr:lun. Sporcntrfiger ziemlich krUftig, kurzllstig.'
According to Sydow, a hyphal fringe along the side of stromatic fruiting bodies,
olive-brown septate spores, and branched conidiophores arc generic characters.
A hyphal fringe persisted in t.ype material studied. b\lt no branched conidiophores
were seen. Wolf and Barbour (41), however, have 1;uggestcd that Sydow was de­
seribing strucl ures that the)' also observed as formed from spermatiferous columnar
cells in spermngonial locules.
\Vhen Sydow described T.Jl!eallosticla p£m: Syd. he was unaware that the same
fungus had been described preYiously by De Thiimen and by Saccardo.
He appears justified in rcnaming the brown spot fungus, because the genlll;i Cryp­
tosporill1n Sacco (24, p. 740) was based OIl a fungus with discoid conical ncervulae
ancl simple hyaline spores.
Later, Sydow obtained a specimcn of Aelinolhyriu7Il morginatum Sacco (\Yeir No.
10330) and noted thnt the fungus ill red areas and Leca710sticta pini Syd. formed
linear stromata, dothicleaceolls in structun', and that bbth fungi produced acicular
spores. He therefore cmended his description to include the fungus in red flecks
in Shattuck's collection (Weir Xo. 10330), Lecanosticta pini Syd. (Weir No.12940),
and CryptoslJOriu7Il ocicolwn Thiim. (l\ [ycotheca Universalis 1484), under the name
Lecanosticta acicola (Thlim.) Syd. (8 t). In this paper Sydow gave a lengthy de­
• P. variabilis is a synonym for P. echinala MiJI.;howc\"cr, thc pine needles are not P. echinala but P. caribaea
Morel. (17).
7 De Thumcn's description may he trnnslatcd as follows: l'erilhecia small, gregarious, in more or less linear
nrrangcmcnt, covered, punctirorm, sub!;lolJose, black; spores cylindrical, sickle,shaped, slightly narrowed
and rounded at both enus, Simple, very Ilumerous, pille brownish gray, 27 X 3.5.-41'. Sooth Carolina:
Afken, in dr~' IC!l\'cs.of Pinu., ,·ariabili. Lamb. (P.1lIitis l\fchx.) (Xo.2072.) Call. II. W, Ra.. enel •
• Sydow (80, p. ilii listed two fJllrntype collections in this description: (I) On P. pallutris, Pike City, Ark.,
collected lJy J. A. 1Tughes (Weir No. 60:12) and (2) OD P. attenuata, Siskiyou Nutional Forest, Oreg., by J. R.
Weir (Weir No. 80(5). 'l'hu pine needles in the former collection appear to be those of P. taeda instead; cer­
tainl}- the botaniC!II distribulion of P. palu$tris does n"t extend as far north as the locality cited .
• Translated as follows: Fruit bouiessingle or several together upon a more or less strongl~' developed basal
stromn of prosenchymatous, rather dnrk-colorcd tissue; soon hreaking forth and becoming entirely super­
ficial; smooth or covered with hrushlike loose hyphae of the fruit body or stroma; opening in 11 wide dishllke
manner: contents arc soft, mOist, of" gelatinous fleshy nature. Spores cylindrical, often strongly hent, with
or without sc\"crnl rather indistinct cross wulls, oli ..e brown. Confdiophores fairly strong, short-branched.
8
TECHNICAL BULLETIN 870, U •. S. DEPT. OF AGRICULTURE
scription of the fungus ill reddish flecks in Sha·tuck's collection.but did not emend
his generic description to include the markedly erumpent hyaline-spored specimen.
Sydow noted that differences in fruiting structure and spore size and shape existed,
but reconciled them by concluding that he was dealing with two stages in the life
history of the same organism, that L. pini Syd. (Weir No. 12940) represented the
mature form, and that the fungus in red flecks in Shattuck's collection (\Vcir No.
10330) represonted an immaturc stage. In describing stromata of L. pini, Sydow
pointed out they attained 60-80),1 in height. In the description of L. acicola
(Thum.) Syd., Sydow noted that the fungus in reel flecks in Shattuck's collection
(Weir No. 10330) produced stromata 160-3':0,.. in height. Even assuming that thc
latter specimen represented an immature stage of L. pini, it is difficult to under­
stand how hard, stromatal fruiting bodies of this size could shrink to 60-80,.. at
maturity.
In 1928 Dearness (7, p. 245), using De Thflmen's name, extended the description of
Cryptosporium acicolum ThUrn. and commented: "While not a typical Crllplospo­
riu7n this fungus fits better there than in Septoria. Its intimate association with
the 'red spot' is ground for suspecting ca,;,;al relation." In 1929 Hedgcock (17,
p. 993) wrote: "This disease was first called by the writer the 'red spot' needle dis­
ease in his notes and correspondence, and this name is used by Dearness (5), but it
is now known by the more appropriate name' brown-spot needle disease' or' brown
spot' . . ." 10
The following pertinent herbnrhuTI specimens were examined in the mycologi­
cal collections of the Bureau of PIau' Industry, Soils, and Agricultural Engineering:
Actinolhyriu1I! marginatw1t Sacc., on P. ponderosa, Orofino, Idaho, colI. Shattuck
(Weir No. 10330); Troy, Mont., call. ,T. R. Weir (Weir No. 19906); "living needles"
(Weir No. 19930) (no further data).
Cryplospor·iwn acicolum Thlim., on P. nigra a1/.slriac~ll;J Lost Springs, Kans.,
colI. L. Pierce, F. P. 20548; 11 Bourbon County, Ky., colI. tl. Garman, F. P. 41675.
Lecanosticta acicola (ThUItI.) Syd., on P. nigra allsiriaca, Oregon, Ill., colI. Roy
G. Pierce, F. P. 18284.
Septoria acicola (Thiim.) Sacc., on P. conlorla, Nelway, B. C., colI. G. G.
Hedgcock, F. P. 54210; on P. montana var. mughu8, Oregon, Ill., colI. Roy G.
Pierce, F. P. 18237; 011 P. nigra auslriaca, Columbia, 1\,10., coli. B. T. Galloway,
F. P. 46791.
None of the fungi in thesc nine numbered collections is Lecanosticla acicola
(Thlim.) Syd. (Cryplosporiu1U acicolum 'l'hflm., Mycoth. Univ. 1484, not Actino­
thllrium lIlarginatuln Sacco (Weir No. 10330». The highly erumpent stromata,
the hyaline sporm!, and a reddish cast, particularly pronounced in the lesional
areas Oll Jleedles of P. ponderosa, are characters sufficient to distinguish these fungi
from L. acicola (ThUrn.) Syd., which normally produces stromata covered at
maturity by the epidermis except for a linear slit and forms relatively wide acicular
spores, subhyaline at first, becoming olivaceous with age (pJ. I, E). The fungns
in reddish lesions in the type collection, A. marginatum Sacco (Weir No. 10330),
described by Sydow (31) for inclusion in Lecanosticta Syd. (80), is excluded by
his generic description.
10
11
Reference (5) In thu quot.ation corr.<;ponds with JJiterlltuTC Oitation (7) in the present mper. Co\lection numbers preceded b~' F.I'. denote specimens on flie in the Diyislon of Forest Pnthology. I,,;OEND ,'on PLATE 1
A, B, and C, AscostronHl,ia of the brown spot fungus. A, Freehand cross section
approx. 40) through Jleedle of Pinlls palustris; the epidermis is ruptured
and rests above the nearly mature ascostromata. Collection made in March.
B, Freehand cross section (X approx. 180) through needle of P. palustris,
showing outlines of asci in median longitUdinal section through locule. Per­
sistence of epidermal and hypodermal tissues above the stroma is due to the
firm attachment between cells of the host and hyphae of the pathogen. C,
Longitudinal section
approx. 60) made with microtome through needle of
P. taeda, showing the epidermis arched above the stroma. This collection of
the fungus, made ill May, shows a mature ascostl'oma with three ascigerous
locules. The conidial stage still persists between the two left-hand locules and
the one to the right. Details of the hyaline contents of the lo~ules al'C not appar­
ent. D, Mature ascospores (X approx. 520) of Scirrhict acicOia (Dean>.) Siggers,
each showing four relatively l.arge brownish oil globules that contra; j' with the
hyaline wall of the spore. E, NOllgerminated conidia (X approx. 2.i:i5) of the
brown spot fungus. P, Germinating conidia (Xapprox. 670), indicating status
of germination on potato dextrose agar medium of pH 5.3, after 48 hours at
~Q
.
eX
eX
T«hnical Bulletin
~iO.
U. S. Departmenl (If All;ricuhutr
PLAU: 1
j)
•
F
,•. ,,).~
tI
,F.al'I's Il, . . . 1
Technical Bulletin $70. U. S. Department of Agriculture
Legend
573337-44
(Fac~s
p. 9)
011
facing page.
PLATE
2
BROWN SPOT NEEDL E BLIGHT CJF PINE SEEDLI NGS
9
Hulbar y has describe d a fungus associat ed with a
blight of P. nigra
aus/riae a Jl1 Illinois as Do/hislr oma pini Hulbary (18).needle
Kamed in Ihe original
uescript ion for genus and species are six collectio ns tha' the
furnishe d from pine needles from Ohio, Iowa, and Oklahompresent author had
that the fungi listed on P. m'gra a1lstn'aca in the nine numbera. It is probabl e
conspec ific with Do/histr oma pini Hulbary , Ill. Kat. Hist. ed collec~ions are
Survey Accessio n
No. 27093.
Hedgco ck (17) used the name Septaria aeicola (ThGm.) Sacco when
he publishe d
the results of his study of the brown spot disease, listing Aetinoth
Sacco find Lccanosticala decipiens Petr.12 as synonym s. Since yn:uln 11larginalu11l
believed that the brown spot fungns could not accurate ly be 1934 the writer has
assigned to Septoria
Fr., because of its strollla! ie structur e and colored spores;
for the sake of cOllsist­
ency, howeve r, he used the name Se7)toria acicola ('l'hihn.)
Sacco until his tax­
onomic stndies could be complet ed (27, 28). Sydow's taxonom
ic treatme nt of
the brown spo' fungus places its conidial sta£;('. ill the patellifo
rm Exeipul aceae
of the Sphaero psidales , alld the writer hus followed Hydo.w's classific
ation.
ASCIGE nO us STAGE
In 1939 Siggers (itO) roported the connect ion between the conidial
stage, .Lccan­
as lie/a ad-coia, (Tltiim.) Ryd., and the ascigel"Ous fungus,
Dcarn. (6), which he transfer red to Sdrrhia ucicola (Dearn. ) asOligostroma adcoia
Olle of the subepi­
dermal, hyaline- spored Phyllac horaceu e. In] 941 Wolf
Barbou r working
indepen dently refelTed the ascigeJ"ou~ stuge io Syslrem maand
the innate-e rulll}len t dark-sp ored Dothidi necae, naming theTheiss. and Syd. in
fungus Systrem ma
adeola (Dearn. ) (41). The gonus Systrel/l ma was erected b)" :!'heisse
n and Sydow
in 1915 (38) for that group of specios in the old genus Dothidea
typified by V. sambuci (1'ors.) I,'r., the !lallle Dolhidea being Fr. (13, p. 551)
discarde d. Since
the genus Dolhidea is one of the oldest and best known
lIumes among the
Dothidi ales uud is the one on which both the family andgeneric
order is bused, Clemen ts
and Shcar (5) and Shear (26), in accorda nce with the recomm
Cambri dge reyision of the Interna tional Code. retained I:he genericendatio ns of the
name Dothidea
with D. sambllci as the type species and relegate d SlIstrem ma
synonom y.
Because clarifica tion of the tuxonom ic status of the brown to
spot fungus was one
of the original objects Qf the investig ation here reported , the
t est his previou s eOllclusioll in the light of observa tions by'" writer desired to
before the publicat ion of the present bulletin . It will be ilotedolf and Barbou r
that these two
taxonom ic treatme nts disagree with respect to (1) group clallsifie
ation of the
fungus ancl (2) pigment ation of the spOl·es.
Accordi ng to Theisse n and 1::iydo,," (33), Clemen ts and Shear (5),
and Blain (1),
the basis for didding the Dothidi ales into familie1; is primari
the stromat a at !Ilaturil y with respect to the host tisHues. ly on the position of
Thus,
Theisse n and Sydow, in the Dothidi iwcac [Dothici cac (6)] are groupedaccordin g to
those forms
in which the mat.ure stromut n are erumpe nt or superfic ial
host. Membe rs of the Phyllnc horacea e [Phylluc holae (5)],011 the surface of the
on the other hand,
12 III lledgeock' R synrmOlJ1Y. tlte ("omhilllllioll Lernlloil!ic
Petrak 1lI11ucd WIIS Lep/Ostrom " tircipit'Jlil l'Nr. (.10,1J.I!I.n. la Ileci]lir713 Petr. is in rrror, os the fungus that
Lf;Of:ND FOil l'J,JTf: 2
.A, Dcn!>e younp; stand of liuplings of Pinus pa!lIstris in northern
generati on Obtained b.,· bUl"Ilinp; the site in Ul28, prior to $C'cci Louisia na; re­
fall. The mild­
ness of the brO\nl spo!, II!"pclle blight from 1929 to 1!J33
d endy rapid
growth in height. HlIb~pq\lpnUy, the diseasp iucrcaRcd illpermitte
\"irulenre and many
ciominant, and olwe thrifty stlplings were ciefoliatC'cl to a height
(01U1.pll1an Forest. Caldwel l Pari~h, La., MtLrch 1939.) 13, Part of G and 8 feet.
of a cOll1mercial
plantat.i on of longleaf pine, illustrat ing Ihe compar ati\'e
develop ment after
10 years in the field of spray('d llnd unspmy NI lots of trees.
saplings had their foliage protecte d from the brown spot by frequenThc thrifty
t sprayin gs
for 6 consecu tive years. In contras t. untreate d seedling s marked
the foregl"Ouncl, 1111>'(\ suffered severe defoliat ions annuall y since by cards, in
ington Parish, La., Februar y 1939.) C, Part of the experim 1929. (Wash­
ental plantati on
of longleaf pine. eslablis hed in the winLer of 1930-31 . Seedling
s on outside
rows were sprn,yecl ] 1 times during 5 growin~ seasons. Most
seedling s in the central row are still hidden in the grass. of the unspray ed
One of the 17
seedling s that were planted in this row has now
growth. (Washin gtoIl Parish, La., Februar y 1.939.) started vigorou s height
5i3337 -44-2
10
TECHNICAL BULLETIN 870, 1I. S. DEPT. OF AGRICULTURE
have innate stromata permanently covered by host tissue, usually forming a
"elypeus" with the epidermis. The clypeus in its typical form consists of epi­
dermal tissue permeated beyond recognition by very dark hyphae. It should be
noted, however, that although the clypeus is characteristic of the Phyllachoraceae
[Phyllachorae (5)], Theissen and Sydow extend the clypeus concept to forms in
which the cuticle covering the stromata is not; in\'aded by the hyphae (33).
In the brown spot fungus, conidial and ascigerous stromata arise subepider­
mally from the periphery of the palisade parenchyma and rupture the epidermis
of the needle by a series of longitudinal slits. Development of the more erumpent
types of sl;romata (ascostromata) often ruptures the epidermis along two parallel
rows, so as to form a strip or band over the fungus tissue. The characteristic
rupture of the epidermis and its superior position with respect to maturing aseo­
stromata of the brown SJlot fungus are illustrated in plate 1, A, B, and C.
These investigations have called for a comparative study of the stromatal
characters of the t,ype species of the genera conccrned. l'-'laterial was obtained
from the mycological collections of the Bureau of Plant Industry, Soils, and .Agri­
cultural Engineering. In the following discussion specimens from the exsiecutue
listed have been compared as to origin of the stromata and theil' ultimate position
with respect to host tissue.
In referring the ascigerotls stage of the brown spot fungus to Oligostroma Syd. (32), Dearness (6, p. 251) described the stromata as " ... senteel in Lhe mesophyll, appearing as short, dark-gray lines under the cuticle . . ." This phmsing im­
plied that the stroma originntes subepidermally and relllaills co\'ered by the host tissue at maturity. Syclow's description (32, p. 265) for Oligostro1l!a 8yd. follows: Oligostromo Syll. noy. gen. l'ln lInchorllecnrllJJ1 (Bt)'m. oliuos \JIlllCnS ct stromu).- Stromn in epiderm/de
situm. I'crithecia (vol pot/us IOl'uli) sub epillerll1itle situ, so iturin, j!lohu\osn, ill1lIlcrsn, porietc bene
ovoluto, ?sLlolo hnud typico [lrncs~nte. Asc npnrllphysoti. Rporidin diclYll1n, hynlillli \"01 snbhynlinn.­
Est qUOS! Pltvllachora hyulodidYlllU. 13
According to Sydow the stroma is seated in the epidermis und the }ocules are
located beJow. Thus, in Oligo,~troma protea Syd. (82, 1). 265), on Pro/en flanigani
(A. Pegler No. 1899, 1915), the type spccies, the efTuKcd stroma is developed
within the epidermal tissues forming a clypeus, and the locules, wholly contained
in the mesophyll, are confluent at their (tpical ends with the epidemlUl stroma.
The ascigerous stroma of the brown spot fungufi is elongate instead anel originates
subepidermally in the mesophyll. As t;he stroma develops upward, the epidcrmis
is arehed by pressure from below (pI. 1, C). The locules, wholly embedded in the
stroma, eventually become exposed, only at Lheir apical cnd~, by a lincar slit in the
epidermis of the needle (pI. 1, A and B). These characters would prevent inclu­
sion of the bro,,,n spot fungus in Olil1o,~t1"oma. Syd.
Clements and Shear (5) relegated Oligostro11ln Syd. to synonomy under Bm'ya­
chOTa FckJ. (16, p. 22u). TheisRen and Syelow classified EU1"lIachora. Fckl. in the
Trabutiineae, a subfamily of the Phyl1achoruceae, characterized by development'
of the stroma between the cuticle and the epidermis.
In Dothirlclln Ihoracella (Rostr.) Sacc., OIl Sedmn maximum (D. Saccardi Mye.
Ital. 658), the type species for EuryachoTa Fclt!., the epidermis of the host appar­
er vJy limits the stroma on its lower sidc and the cuticln on the upper. The locules
are embedded centra1ly in the middle of the effused stroma. The stromata of
this fungus couJdnot be confused with that of the bro\\'.11 spot fungus. In Dothidea
sambtlCi, on Sambucus nigra (specimen in the mycological. co1lcctions, Bureau of
Plant Industry, Soils, and Agricultural Engineering, co1lected by Gunnar V.
Sehotte, HI. Vapno, Fungi Scandinavici, July 1893), the type for ])olbidea Fr. and
Systremma Theiss. and Syd., the markedly erumpellt pulvinate stromata lack
epidermal cover, in contrast with the distinctly superior position of epidermal
tissue as shown in sections through stromata of the brown spot fungus (pL I,
A, B, and C).
Fuckel's original description for Scirrhia Nits. (15, p. 220), like many of the early
generic descriptions of fungi, was very brief and included characters not possessed by
Scirrhia rimosa (Alb. and Schw.) Fck!., the type species. The ascigerous st.age of
the brown spot fungus, however, agrees well with Theissen and Sydow's emended
description for Scirrhia Nits., except that a elypeus is lacking.lI Similarly, Scir­
rhia rimosa on Phragmites sp. (Jaczewski, Komarov, Trallzsehel, F. Ross. Exs.14.0)
II Translated as rollows: Olioo~troma Syd. nnw genus Phyllnchoracearum (etymolollY oli"", littlo and
stoma).-Stroma situated in epidermis. Peritheela (or rather loculi) subepidermal, solitnry, globose,
Immersed, wall appears well.developed\ ost/ole not typically present. Asci without paraphyses. Spores
2.rclled, hYRline or subhyallne. It is n most Phyllachora hya[odidyma.
\I Theissen and Sydow's emended description or Scirrhla Nits. (39, p. 41S) may be translated as rOllows:
Stroma linear, placed superfiCially under the epidermis, covered by an epidermal clypeus nnd grown together
with it, constructed or vertically parallel prosenchymatous tissue. Loculi in longtudinal rows, tearing the
co\'er at the top, whereby a linear slit Is rormed. Spores two·celled, colorless.
BROWN SPOT NEEDLE BLIGHT OF PINE SEEDLINGS
11
is nonclypeate, but the upraised epidermis gives a clypeate appearance. Classi­
fication of Scirrhia Nits. in the clypeate PhyIIaehoraceae may have come about
because Theissen and Sydow (33) distinguish\ld the genus on the basis of its sub­
epidermal stroma.
In stromatic characters the ascigerous !ltage of tihe brown spot fungus has more
in common with Scirrhia ri1llosa than with any of the other specimells studied.
The following points of similarity are evident: The elongated stromata, which
originate in the mesophyIl, the upraised but persistent epidermif;, the well-devel­
oped vertically parallel pseudoprosenchymatous tissue, and thc capacity to pro­
duce thc conidial and ascigerous stages from the same stroma. It should be noted,
however, that S. rimosa has simple globose conidia and that interascicular pseudo­
parenchyma reported by Blain (1) for S. ri'lllOSlt docs not occur in the brown spot
fungus.
Wolf and Barbour (41), in referring the brown spot fungus to S1JstremmtL acicola
(Dearn.) Wolf and Barbour, have ascribed color ("dilute brunneolis") to the IlSCO­
spores, whereas Dearness (6) and Siggers (Z9) described them as hyaline. As the
latter baRed his description on viable spores from crushed ascigerous locules, it
was thought that spores discharged from the ascus might prove to be colored.
Spores discharged from the ascus when compared with spores from crushed fruit­
ing bodies showed no intensification in color. Color in the mature ascopore is lim­
ited to part of the spore contents, i. e., the four large amber-colored or brownish
oil globules (pI. 1, D). The integument or spore wall is hyaline or subhyaline,
depending on the source or kind cf light uscd. If one considers that spore color in
this instance is determined by color of only a part of the contents, ascospores of
the brown spot fungus are dilute brown; if One regards spore color as determ\ned
by eolor in the epispore, the spore wall, the spores are hyaline.
In conclusion, the ascigerous stage of the brown spot fungus agrees well with the
description for SC'irrhia Nits. as emended by Theissen and Sydow.. In stromatic
characters the brown spot fungus approaches the type for Scirrhia Nits. more
closely than it does allY other type specimen studied, and the hyaline spore wall
permits inclusion of the fungus in that genus.
SPECIlIIENS EXAlIIINED
Ascigerous stage.-Herbarium, Division of Forest Pathology, Bureau of Plant
Industry, Soils, and Agricultural Engineering, on Pimls palustris, Silver Springs,
Fla., call. G. G. Hedgcock. F ..P. 32146 (t,ype call. of Oligostroma. acicola); Helena,
Ga., call. G. G. Hedgcock, F. P. 17627; Durham, N. C., call. Carl Hartley, F. P.
50000; ·Woodworth, La., call. Paul V. Siggers, F. P. 50001; Urania, La., call. Paul
V. Siggers, F. P. 50002; Bogalusa, La., call. Paul V. Siggers, F. P. 50003; Brooklyn,
.1\1:iss., call. Paul V. Siggers, F. P. 50009; on P. laeda, Fordyce, Ark., call. Dale Chap­
man, F ..P. 50004; Rusk, Tex., call. P. A. Young, F.P. 5000,); all P. thunbergii, Camp
Pinchot,Fla., call. Paul V. Siggers,F. P. 50006.
Conidial stage.-(The first four specimens cited below are in the mycological
collections of the Bureau, and the rest in the Herbarium of the Division of Forest
Pathology.) Thlimen, Mycoth. Univ.1484 (ex-type of Cr1Jptosporimn acicolum);
on P. attenuata, Siskiyou National Forest, Oreg., call. .T. R. Weir 8057; on P. taeda,Pike
City, Ark., call. J. A. Hughes Herb.•J. R. Weir 6632; Herb. ,J. R. Weir 12940 (type
call. of Lecanosticta pini); on P. caribaea, St. Petersburg, Fla., call. G. G. Hedgcock,
F. P. 80595; onP. contorta lati/olia, Waterloo State Forest, OhiO, call. C. C. Green,
F. P. 50007; all P. glabra., Gainesville, Fla., call. G. G. Hedgcock, F. P. 32112;
Gainesville, Fla., call. G. G. Hedgcock, F. P. 17489; on P. palustris, Conecuh National
rarest, Ala., call. Howard Lamb, F. P. 50010; on P. ponderosa var.JejJreyi, Water­
loo StateFores~ Ohio, call. Ovid Alderman, F. P. 50008; on P. rigida, Conasauga,
Tenn., call. G. u.Hedgcock, F. P.43036.
HOST RANGE AND GEOGRAPHICAL DISTRIBUTION
'rhe brown spot fungus has been found on 24 species or varieties
of pines, including the hybrid sonderegger pine. In recent years
many species of pines native to the West have been introduced as
regional exotics into southern nurseries where the disease is
usually present. N early all collections of the fungus on western pines
have been made in nurseries in the Gulf States.
In the .East the disease has been found in all coastal States from
North Oarolina to Texas and inland in Arkansas, Tennessee, and
T.ECRNICAL:SULnETIN >87,O,TJ.:S. 'DE~. OF 'AGRICUtTURE
·Ohio. 'In ithe'West. it is found :insouthwestEim 'Oregon. ·.'Fhenorth­
.em, limits· of .thegeograpbicaI di'!trillution of· the fungus are ,not well
defined. The writer believes 'that the brown spot fungus, extends
northward in the East us far as Pinus echinata and P. 'taeda OCCUl'RS
forest trees. The following list gives the known distribution of the
pathogen by States for each pine host and is based on collections in
t9.eDivision of Forest Pathology at Beltsville, Md., and at New
Orleans, La.
Host
State! in which coUected
.Pinus attenuata Lemm.l~ ___________ . _____ _ Florida, Louisiana, Oregon.
P. caribaea MoreU_.____________________ _ Florida, Georgia, Louisiana, Mis­
sissippi, South Carolina, Texas.
P.contortavar. latifolia S. Wats. (P, mur­
rayanaBalf.) 1_____________________ Louisiana, Ohio.
P. coulteri D. Don 1 _____________________ Florida, Louisiana,.
P. echinata.Mill.2_~ ______________________ Alabama, Louisiana.
P. glabra WalK' ________________________ Flor~da.
P. halepensis Mill.I ______________________ Florida. P. latifolia Sarg.l_________ ~ ______ ~_~ ____ Florida. P. nigra poiretiana (Ant.) Asehers. and
Graebn. 1__________________________ Louisiana. P. muricata D. Don 1 ___________________._ Florida. P. palmtris Mill. 2 _______________________ Alabama, Flori'da, Georgia, Louisi­
ana, Mississippi, North Carolina,
South Carolina, Tennessee, Texas.
P. pina8ter Ait.I_________________________ Florida, Louisiana,
Mississippi,
Texas.
P. pinea L.1 ____________________________ Florida.
P. ponderosa var. 8copulorum Engelm:l _____ Florida, Louisiana, Tennessee.
P. ponderosa var. jejJreyi Vasey 1 __________ Florida, Ohio. P. radiata D. Don I _______ . _____________ Florida, LouiSiana. P. rigida Mill. 2__________________________ North Carolina, Tennessee. P. ri.gida serotina (Miehx.) Loud. 2 _________ Louisiana. Psabiniana Dougl.1__ ~ ________ ~ _________ Louisiana. P. 80ndereggeri Chapm. [hybrid] 2 __________ Louisiana. P. strobus L.2 _______.__________ ~ _________ North Carolina. P . .taeda L.2_______ ~ _____________________ Alabama,
Arkansas,
Georgia,
Louisiana, Mississippi, North
Carolina, South Carolina, Ten­
nessee, Texas.
P; thunbergii Parl. 1 ____ ~ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Florida, Mississippi.
P. virginiana Mill. 2______________________ Georgia, North Carolina.
I
Occur as exotics in the East.
'Native to the Southeast.
Hedgcock (17) recorded the brown spot fungus on P. nigra austri­
aca.from Kansas, Kentucky, and Missouri, and on P. ponderosafr.Qm
Idaho, apparently on the basis of four of the nine numbered collec­
tions of hyaline-spored, pine-needle fungi listed herein lmder taxonomy
oithe imperfect fungus. As these fungi have characters that prevent
their inclusion in the genus Lecanosticta Syd., it suffices to say tha.t
the brown spot fungus is not known to occur in these States.
CULTURAL STUDIES
A critical physiological.inv.estigation of the brown spot fungus wa~
.never attempted, siI.lce by nature the pathogen is .not a favora~le s¥b­
'ie.pt. :for physiological stUd.ies, as it germinates .ana gr.o.ws.. slow.Jy';in
culture. The cultural work here ;reported was limited to a.studY,Qf
the effect of some factors of. the environment on,germination andtn,e,
s:ubsequentgrQwth and fructification of the organism. ThewfJrk~as
-done'to help determine'what factors or .set of environmental COJ1lli~·
BROWN SPOT NEEDL E BLIGHT 01<' PINE SEEDLI NGS
13
tions govern the varying. severit y of the disease in nature and to find
the explan ation for consistently negativ e results obtain
ed from
inoculat·iolls.
MATER IALS AND :METHO DS
The potato dextrose agar used in cultural studies was all made
up at the same
time and prepare d as follows: 300 grams of potatoe s were
cut and boiled and the
extract filtered off after 20 minutes . To this extract were added
15 grams of agar,
10 grams of dextrose , and sufficien t distilled water to make 1,000
cc. After ster­
ilization at 15 pounds' pressure for 20 minutes , the medium
sterilize d at 10 pounds' pressure . The pH, as determi ned was tubed and re­
by the colorim etric
method , was 5.8. The reserve alkalini ty (0.525) and
reserve acidity (0.400)
indicate d that the buffer index was 0.925 for the rangethe
FH 4.0 to 8.0.
Throug llout the cultural work the develop ment of the fungus
was studied in
Van Tieghem cells 4 mm. high and 15 to 18 mm. ill diamete
r. The rings rested
directly over holes cut in filter paper in bottom of Petri dishes
100 mm. in diamete r or 15 mm. in depth. The holes in the paper not less than
let light come
from below and permitt ed direct observa tion of the eells under
In the prepara tion of a culture, a drop of agar was placed centrall the microsc ope.
and this was then inverted over its glass ring. Distille d water y on a cover slip,
added to the filter paper to prevent the agar from drying out.
was immedi ately
For single-s pore manipul ation, two microsc opes were used.
out at one end to microsc opic diamete r was fixed at its other
A glass rod drawn
end to the tube of
one instrum ent, and a mass of spores on a drop of agar was placed
in a damp cham­
ber on a slide resting in the mechan ical stage of a second microsc
ed discussi ons of t.he techniqu e of spore isolation , referenc e is ope. For extend­
made to papers by
Hanna (16) and T;ickillson to).
Spores were transfer red singly or in mass to the Van Tieghem
cells, dependi ng
on the purpose of the test and the source of spores. For instance
, in a test of
spore vitality as related to the period elapsing since collection.
of infected needles,
it was necessa ry to isolate each test spore to avoid the bacteria
l and fungal con­
taminan ts usually present on nonsteri lized fruiting bodies.
In other tests, ex­
uded spores from pure culture were merely shifted from the periphe
ry of the spore
concent ration to vacant areas on the same drop of nutrien
t agar. In a third
experim ent, spores were transfer red in mass and germina tion permitt
ed without fur­
ther disturba nce of the inoculum . In this case, record
germina tion was based
only on those spores lying directly on the surface of theofagar
and periphe rally to
the mass of spores.
Except as otherwi se noted, cultures of the pathoge n were kept
at room tem­
peratur e and maintai ned in an atmosph ere close to the moistur
e saturati on point.
An electric refriger ator and an electric heat-con trolled incubat
or were used for
the tempera ture studies. In the refriger ator, high humidit
ture 'Contras ted with low humidit y and high tempera ture iny and low tempera ­
was not possible with equipm ent availabl e to run tempera ture the incubat or. It
tests at 20° C.
In all tests the cultures came from conidia produce d in mature
pycnidi a. Ex­ cept for the germina tion test with spores from infected pine
needles, tbe pycnidi a
carne from monosp orolls conidial cultures . As it was impossi
perimen ts simultan eously, the pathoge n was reisolat ed from ble to start all ex­ of needles, in order to have a supply of spores in cultures readythe same collectio n
for testing. The
source of the spores was the same in each t&st, but differed
usually between tests. SPORE GERMIN ATION
Separat ion of viable spores from their sticky matrix to a suitable
eIlviron ment
usually instigat es the process of germina tion, In culture,
spores have occasion ­
ally germina ted in situ. Physiolo gical maturit y, howeve r, is
prerequ isite to ger­
minatio n and follows the septatio n process. At
time of germina tion
the entire conidiu m or 011e or more of its cells becomesthe
bloated (pI. 1, F). Germ
tubes may appear at any time from the fourteen th to the
fifty-sec ond hour after
conidia have been transfer red to nutrien t agar.
TEMPER ATURE RELATI ONS
In each tempera ture test 100 spores were obtaine d by separati
a spore mass in each of 10 Van Tieghem cells. Germin ation ng 10 spores from
tests were run from
5° to 35° C., inclusiv e. 'l'he effect of tempera ture as a factor
in germina tion is
indicate d in table 1.
The minimu m tempera ture for spore germina tion apparen tly lies
10° C. .l\.lthough 5° totally inhibite d germina tion during the between 5° and
test period of 72
14
TECHNICAL BULLETIN 8'70) U. S. DEPT. OF AGRICULTURE
TABLE
I.-Germination of spores at dii[erent temperatures on potato dextrose agar
I
.~pptoximate
.~ge of culTemperature tures from
Test perioo
range
which spores
came
temperature (" C.)
5•••__• '. ___ .___ ._._____ ....... --.----.--- ....
10._____ ....__ ._.________ - ---------------.-15.__ ..________ ._._____ ••--....- .• -----------25•.
• ___••_--. --. ---. -- •• -. -.-- •. --....-- - -30__•_____
____ • __
•__•••_________________••________
35 _________________ .• ___..__ • ______ ------.-- ..
• C.
4. &- 6.0 9. &-10. 5
14.1-15.5
24.8-2,5.4
29.&-31.0
34.;-36.6
DaU3
P<rctnl
Houn
18
28
19
17
16
19
Germination
12
il
58
31;
fi2
6;
0
100
93
100
lCO
0
hours, 56 percent germinated within 16H hours after being transferred from 5°
to laboratory conditions. The maximum temperature for spore germination is
apparently below 35°. At the end of the observation period at this temperature
.a number of the spores were swollen, a condition suggesting that the maximum
temperature that inhibited germination was only slightly below 35°. That the
spores were viable when placed in the incubator is indicated from the result of the
germination test run concurrently at 15°. Both lots of spores came from the
same spore mass. MOISTURE RELATlONS A mICroscopic filin of water on the surface of a. drop of agar in a moist Van Tieghern cell js sufficient for germination. Likewise, germination may occur on agar under a droplet of condensation water. No constant humidity chambers were available for this study, and it was not possible to determine the effect of different humidities on gcrmination.
When stored in lhe relatively dry atmosphere of a laboratory it was fOUlld that
spores from infected pine needles soon began to lose the capacity to germinate.
On September 10, 1938, a collection of diseased needles of P. lh1.lnbergii was made
in Florida and brought to New Orleans. The collection was divided 2 days later
into two lots and placed in separllte envelopes; olle was kept in darkness in an
electric refrigerator at temperaI ures between 5° and 15° C., with humidity about
80 percent, while the other was kept on top of an oflice desk subject to the daily
and seasonal fluctuations in indoor temperature and humidity that, occurred
between September 12 and December 19, 1938. Temperatures in the room during
this period varied between 60° (15.56° C.) and 93° (33.89° C.) F., and humidities
between 25 and 90 llercent. Record of room temperature and humidity was kept
daily with n Friez hygrotherll10graph, beginning October 27 and ending December
14. Durio!: this latter period the daily maximum room temperatures exceeded
830 F .. (28.33° C.) OJ) 4 days, while on 3 days the daily minimum fell below 66° F.
(18.890 C.). The daily maximum I'ela. ive humidities were usually below 65 per­
cent.
Germination tests, starting 5 days after needle collection, were continued at inter­
vals until 100 days had elapsed. All tests were made under conditions favorable
for germination. Except for the test at 100 days, each spore was isolated io a Van
Tiegliem cell to.reduce the chance for contamination from the non sterilized fruiting
body. \Vith age of the spores unknown, each fruiting body used as a source of the
inoculum was selected on the basi:'! of apparent nlaturity, as indicated by the dark
pigment (due to the underlying spore mass) and slight ruptnre of the epidermis.
Results of germination tests, as detailed in table 2, indicate that spores are
short-lived when kept under room conditions as compared with longevity of
spores stored at low temperatures and high humidity. This test suggest.s that
the desiccating effect of high temperatme and low humidity or their variations
exerts an important influence on vitality of spores in mass. Possibly loss in
vitality is due to a progressive reduction in spore moisture content.
LIGHT RELATlONS
Preliminary germination tests made in daylight over an extended period showed
that diffuse light exerts little if any deleterious effect on germination. No tests
werc made to determine whether light influences the time of germination.
HYDROGEN-ION RELATIONS
When used in field tests as a spray to control brown spot, calcium caseinate
(casein spreader) mixed at the rate of two-thirds of an ounce to a gallon of water
15
BROWN SPOT NEEDLE BLIGHT OF PINE SEEDLINGS
TABLE
2.-Viamlity of conidia of the brown spot fungus after varied period8 of
storage under different artificial conditions
I
i
Spores tested from
Germination o f '
Spores tested from
Germination of
Number needles stored inspores from,Number I needles stored inspores from­
of days -------~-------:-----~c_.-----! ~fdays ,______~------.I-----~._----slnce,col.
, Since col·
J
leetion of Refriger'
Open
R~friger' Open 'Iection of Ii Refri"er. 9pen Refrigcr' Open
ator
IsbaIsba· I needles'
~
,abo·
'
laho·
needles I
ator
ratory
ator
rstory
ator
ratory
ratory
I
---------------1---:----;-------Number
5•• __•••_...........
10••••••.•.••••.••••
IS••••.••• _.•_••••••
21 .... _. __ •••••••.••
25 •••••••_ ..........
Number
30 •• _•••• __._ ••••• _.
36.___..__ • ___ ••••_.
• Needles wero
plac~d
Percent
13
20
Percent
I
I
+-........
Number I' NlLmber
40 __ ".24
77
40
48, .....
1
76
5,1 .. " •••, .... _.•••• \
23 .flO·" .... i
19'
29
9",
32
60
lOO"""-r'-'
25
30
35
40
20
o
---I
35
Percent
Percent
50 ' •• '''''_'
29
94
11'····· '..
---I
,
s.~
38
11
au
0
0
f>8
liS -....... ,.
14
1
mule. the 2 storage couditious all thn third day.
and calcium hydroxide mixed at the rate of 1 ounce a gallon strikingly reduced
the e~-tent of infection. The following test was undertaken to explain the effect
of lime sprnys on field infection and to determine what degree of alkalinity or
acidity inhibited spore germination.
Small quantities of approximately N/20 ;solutions of sodium hydroxide and
of hydrochloric acid were added to tubes of tllfl (!ulture medium. Acid and alka­
line media were obtained covering a pH range of 4.3 to 9.1. Fifty spores were
separated from each spore mass planted on the surface of drops of agar of known
pH and were incubated for 48 hours. Record was then made of the number of
spores in each lot of 50 to germinate. Spores germinated abundantly on all acid
agar and on basic agar up to pH 8.3. Agars with pH 8.9 and 9.1 totally inhibited
germination. The alkaline limit for spore germination lay between pH 8.3 ana 8.9.
Calcium caseinate, which cOJllmonly contains 80 percent finely ground calcium
hydro};ide, gives a pH reaction of 9.6 when added to distilled water at the same
rate at which it was mixed in the field. Solutions of calcium caseinate or calcium
hydroxide, when. used alone as a fipm)" reduced needle infection by forming a
coating on the surface of the needles sufficicntly alkaline 1;0 inhibit spore germi­
nation.
GnOWTH
TE~U>EnATUJtE
RELATIONS
The usual method employed by investigators dealing with external factors
affecting fungus growth is to cut small disks or squares from the advancing margin
of a stock culture, tran8fer them to the surface of agar in Petri dishes, and expose
the inoeula to a specific environmental condition. The slow growth, however,
and the growth habit of the browll spot fungus made it necessary to discard cus­
tomary technique and bcgin with recently germinated spores, measuring the rate
of growth by means of an eyepiece micrometer and an adjustable mechanical
stage. In these measurements the initial lengths of the germ tubes were consid­
ered negligible. A fruit body from a different culture was used as the source of
spores in each test. Ten single-spore colonies were used at each of five different
temperatures. The average diameters of the colonies at the end of 2 weeks are
given in table 3.
TABLE
3.-Average diameters of colom:es of the brown spot fungus after £3 weeks'
incubation on agar at different temperatures
Irrcrnpt!r6t.un~'I
li---------'------­
Period.spores!
." pproximllte temperature (OC.)
I
5. __• ___ •_____ •____• ___ ._ ..... _•••••.•.•. , . . _
10.._•••••••__.._________ • ___ ••• _... __ '. - '. __ _
15_._______.. _._. _____••••••• ___ . •.• ••..• __
25. __ . ____ ,,__, ___ , • __ ,,. __ • __• ___ ._ • • _'. _••__
30_________ •____________________ •_____ . __• __ ._._
range
~
° C.
4.5· 5.5
9.5-1'1.5
14.1-15.5
24.8-25,4
29,0-31.0
')':ach llgurn is an averngo.of 10 c9Ionins}Hc.·i)~ for the fnurth
were mC.ll­
bate.j
prtor
to st:i;ing
Haun
45
42
46
61
51
~roup
I
Dirullcter of colonies '
l\Inan
Rlln~e
ltfillimelers
lIfillimtltr,
O.08±O.OO5
1,5:1± .1~8
l.if.± .074
2,G5± .200
1.80± .070
(25°), which
W.lS
0.06-0.12
.79-2.13
1.42-2.03
I. 65-3. 47
1.42-2.02
for 9 colonies.
16
TECHNICAL BULLETIN 870, U. S. DEPT. OF AGRICULTURE
LIGHT RELATIONS
To determine the effect of diffuse light on hyphal growth, 15 spores, each iso­
lated on agar in a Van Tieghem cell, were placed· in a Petri dish, which was in turn
enclosed in a larger "moist chamber" cultur r dish. The inner dish functioned
as a trayj the outer, which had been paint,:.i black, served to exclude light. In
the same manner, an equal number of single spores were placed inside 2 similar
glass containers, both of which were unpainted and permitted the entrance of
diffuse daylight. The 2 lots of cultures, one in darkness and the other in light,
were kept side by side on a laboratory table near a window at room temperature.
The agar used in both scts of cultures came from the same tube. The spores
came from a fruiting body in a 27-day-old culture. Before starting the experi­
ment, the effectiveness of the coat of black paint was tested with photographic
film and found to be satisfactory. Both sets of cultures wer" kept moist by adding
water at night, 3 times during the observation period.
After 20 days, measurements of 29 cultures w(:re made under the microscope
with an eyepiece micrometer and an adjustable mechanical stage. The average
diameter of 14 cultures exposed to dHfuse daylight was 2.5!) mm., whereas that
of 15 cultures kept ill the dark was 2.55 Illm. This difference is without statistical
significance.
FRUCTIFICATION
TIME UELA'l'IONS
Monosporolls cultures kept in strong diffuse light at room temperature produced
primordial fruiting bodies about the eighth to the tenth day after inoculation. At
maturity, these bodies are dark brown to blackish and relatively hard. Frequently
the pycnidiaarejoined in the same stromatic mass. filature conidia have developed
in eulture in a minimum of 14 days, although about 20 days are usually required.
LIGUT UELA'rIONS
Small but constant redllcti0ns in average foliage infection were indicated m
field-plot testsasareflult of the use of artificial shade. It is possible that this reduc­
tion was due to the direct effect of shade on fructification of the fungus. The same
cultures that had been used to study the effect of diffuse light on hyphal growth
served for a study of the effect of Jight on fructificai ion of the fungus in the labora­
tory. As indicated in tablc '1, in 14 clllillres kept in the li~ht 13 pycnidia had
formed as compared with S in the 15 cultures in the dark chamber. The difference
was only 1.16 times its standard error when figured in the usual way. Although
this analysis indicated that the differences are not statistically significant, had the
same type of frequency distribution been maintained for a greater number of
observations a significant difference could have been dcmonstrated.
TABf,E
4.-/l',uctification oj the brown spotj1mglls on agar in diffuse light and in
darkness
'
I
Ii
Culture'S with nurn·
ber of prcnidin- :1
"
Number of pycnidin per
cullUm
, In light
f
- - - I J.\ umber
I,
:
T
I
7
1_ ••• _•• _...... _..............
2!
2...................... .......
ness
_
0......... _._ ••• __ .. ____ • __ ••.
3••.••• _. __ ...................
In dark·
4 i
1 •
!
.1\ lL11Ibrr
Iii
~umbcr
of pyclIi.1in pcr
culture
with num­
!! Cultures
l)cr of pycnidia-
r.
11-----·
Ii
I
!
In Ii"ht : In dark·
r>
I !Yumbcr
:
ness
i
r ,Nkmber
!
15 !I Numbcrof cultures ........ ,:1 -1314 -­
2: 'I'otnlnumbcr of pycnidin .'
8
9
·1
0
IIII 1I1('unnllll1bcr
of pycnidin
!
pcrcuiturc................
J
0.93
I
0.53 Su~mARY OF CULTURAL STumES
Temperature and moisture seem to be the chief factors influencing spore germC
nation. The upper and lower thermal limits for germination were found to be ap­
proximately 35° and 5° C. The optimum temperature for germination appears to
be between 25° and 30°. Storage in a relatively dry atmosphere rapidly reduced the
percentage of germination, possibly because of the physiological effect of progres­
BROWN SPOT :NEEDLE BLIGHT OF PINE SEEDLINGS
17
sive reduction of the spore moisture content. Diffuse light exerted no effect on'
germination. The alkaline limit for germination lay between pH 8.3 and 8.9; the
acid limit for germina< ion was below pH 4.3.
Diffuse light exerts no influence on growth. The minimum and ma.ximum tem­
peratures for growth appear to be slightly below 5° and about 35° C., respectively.
The optimum temperature appears to lie between 25° and 30°, closer to the former
than to the latter.
With favorable environmental conditions, the brown spot fungus started to form
fruiting bodies in single spore colonies in 8 to 9 days und produced mature spores
in a minimum of 14.
Light appeared to stimulate fructification, reSUlting in a higher average number
of fruiting bodies per colony.
INOCULATION EXPERIMENTS
Several years ago Dr. Eugene O. Tims, associate plant pathologist,
at the Louisiana State trniversity, in a letter dated January 14, 1931,
wrote with reference to the pntllOgclIicity of the brown spot fungus:
I had the causal organism in pure culture on numerous occasions and obtained
conidial production quite regularly during 1925 and 1926. The conidia did not
germinate, however, on any medium used except prune agar and prune decoction.
Dr. Edgerton first obtained infection with pure cultures of the fungus in 1923.
I mude a number of inoculations on young slash and longleaf pine seedlings
which were successful. I sprayed the needles with an aqueous suspension of
sporer:. and then covered the needles with moist chambers for 48 hours. Small
spots appeared on the needles about two weeks later. The fungus was suc­
cessfully reisolated from such typical spots.
In preliminary work on September 23, 1938, without controls, the
writer sprayed brown spot spores formed ill culture on the healthy
foliage of 10-month-old seedlings of longleaf pine growing in llutrient
solution. The seedlings had been raised from seed on the porch of a
New Orleans rcsidellce. The plants wer£' coYered with paraffine(l
paper until September 30. Ol'dinarymncllllU' Jesions Ilnd bar spots
were noted on October -1-. An exuded SpOrt· mass was Jound October 7
on a fruiting body Jormet! in one of tIll' mneulur lesiolls. The infected
Ileedle with the fruiting body that produced the muss of exud('d spores
wns removpd. to thl' laboratory OIl December 4. On the same day
35 single spores W01"e Lrnllsferrecl from the spore mass to nutrient ngar
ill Van Tieghem t;cl1s, und 28 of these gennil1[Lted. The spores thnt
camc from this mnss Wel"(' similnr in size, shape, nnd color to brown
spot conidia formed 011 pine need1es in nature. Four attempts, with
controls, we!"(' mnde Inter to illOl"ulate healthy 10nglenJ piile seed­
lings with the brown spot Jllne:,os, but. without success. A possible
cxplutH'Ltion for the negative results mn,y be the tenl1city with which
conidia of the fungus, even 'when in water, tldhere t.o glass nnd other
surfaces. Glass atomizers nnd other eqldpment were employed to
transfer the spores, and probnbly little inoculum ever renehed the
pine lIeedles.
DISSEMINATIOK O:F THE PATHOGEN
Disseminntion of 8}JOl'CS of the fungus, us affected hY'the ngency of
rain or wind, wns ohserved bY' exposing glass microscope slides in a
very dense stand oJ longleaf pine reproduction ncar Bogalusa, La./ 5
when' the virulence of the' diseuse has long been rceognized (10,38).
Most; of the conidin. that Jell on the slides al'e known to hn\'(' come
" Thc first rcport, In U. S. Bur. Plant indus., PIUDtJ)ls. Hptr. Slip. 37: 353. (1925). of th~ occllrrcllcl' of the­
dlscascln LouisiaDa wns made by lIfi~ Anna E. I.ekins, frolll n Bo~niusn, Ln., rollection,
573337-44-3
18
TECHNICAL BULLETIN 870, U. S. DEPT. OF AGRLCULTUHE
from lesions produced on foliage growing in a ZOIW 2 Lo 12 illchl's
above ground. PrelimiUlu'Y slide-exposure trials hegun May 25 to 2i,
1936. Thereafter, slides in seLs of 11 to 15 were exposed consecu tively
from June 15 to August, 14, 193fi. From Srptcmbcr ], 1937, to Jan­
uary 1., 1.938, slides in sets of 6 were exposed horizontally below the
level of infected pine lIeedles on a lath that rested on the ground. III
concurrent tests tl1{' same number of slidrs \\"r1'r placed in l1otchr8
cut at iutervnJs of 1 foot 011 a vcrtic(Ll wooden stun', l'he lowest slide
on the stafr, at a height of 1. foot, WfiS on tl1<' sallH' level with illfeclrd
foliage, but not ill contact with it. The other slides were above the
level of the nerdles. This IU'L'angement permitted compn,rison brtwerll
horizontal find vertienl dispersal of spores.
Glycerine 'WtlS usrd fol' n, spore adhesive. After eXpOSlll'<', spo]'r
counts were made on n, 0.2446 square-inch fire a of the glycrrinrd sur­
face of each slick. Thr Itrrtl, rXlLminrd OIl r[loh slide was abou t one­
twelfth of tl\(, lotal surTner.
DISSElIllNATION OF CONIDIA AS RE],A1'ED TO ~lETEOROLOr.'CAL CONDITIONS
That rain is an important fact·or in the dissemination of conidia is indicated by
table 5, where the main variables considered arf' rainfall compared with number
of conidia for each period of exposure.
The mcteorological data given ill labl€' 5 werf' taken at the Weather Bureau
Station, ,Bogalusa, La. Although til(' record there docs not accurately present;
the weather conditions at, the ,:lide-exposurc station, it gives the uest meteoro­
logical information a\'ailable, The followin~ discussion is based at the assump­
tion that the meteorological conditions at thf' two places were similnr but not
identical.
RAIN srI,ASH
'Vater in the form of min splash iti the main factor ill til(' dissemination of co­
nidia, and in its absellce Iittln (Tansfrr of infective material takes place. The
physical action of rain in spore dissemination con~ift" in first washing the spores
out of their sticky matrix and then in tral\~planting them in splash droplets from
thcir place of production to other needle::;. Heavy dews arc probably important
in the local dissemination of spores from infected to healthy parts of the same
needle. Hard rains when the spores arc exuded \vould be expected to wash much
of the inoculum to the ground before it; has had time to dry and become attached
to the susceptible parts of the host. In two instances, on :i\1ay 27, 1036, and on
October 7, 1037, wideeprcad dissemination of conidia took place when a light rain
had followed several days of rainy weather. The heaviest spore shower on
record took place between 8 a. Ill., October 5 and 5 p. Ill., October 7, 1937, a pe­
riod preceded by '1 days of rainy or cloudy weather.
WIND-DT,OWN n,I..[N
In 'a study of the dissemination of the angulnr leaf spot of cotton, Faulwetter
(11) mcaslITcd fhe dispersal of splMih dl'oplet~ as influenced by wind. Under the
experiment;ai couditiolls, he fOllnd that splash could be carried to a maximum
horizontal distance of 18 fert when drivcn b\' 3, wind of 10 miles nn hour and that
in the absence of wind the impaet of drop~ on u nonclevated horizontal surface
carried splash droplets as far us 56 inches. In nature, the impact of drops 011
the foliage of smull longleuf pine seedlings would not, be expected to carry splash
as far as Faulwettcr observrcl experimentally, because the narrow surfaces of
impact (needles) afC wiually only slightly elrvatec\ and partly surrounded by grass.
In the present study, the effect of wind-blown min 011 dissemination of the
brown spot fungus waR tested by placing slides horizontally on the ground in a
fire lane that had been bllrnrd in Febl'llary 1036. Three sets of five slides were
each exposed consecutively betweell 6:30 'p. m., May 25 and 7 p: m., ?lIay 27,
1936, and so placed that nono was closer to an apparent source of lIloculum than
8 feet. One spore was found 011 a slide that had been exposed 12 feet from the
nearest margin of the firo lun!' during a light rain on the afternoon of ]\IIay 27.
19
,BllOWN'SPOT NEEDLE BLIGHT OF PIN.E -SEEDLINGS
5.-Relation of rain /0 dist.emination oJ conidia of the brown spotfangus, as
de/ermined by number 'o.f sp01'e8' observed on glas8 slides exposed in an area. of '
SIWC1'e inJection
'
'1;ABT,E
.
Dnte slide expORure
began
'I
~:W'
dnring
expo~nrc
pcnod
SPOICS prorated per square inch oC slide area 011 slides exposeti­
I
I.
Vertica\ly above or on same level with InCected Coliage
norlzon· .
~:l~~· I
Distance above gronnd (Ceet)
Infected _.___._._ _--,_ _ _""""_ _--,_ _ _-,-_.___
Coliage
I
1
,•_ _
4 ___
5 _ ,_ __
f)
_ _ _ _ _ _._._ _ _ _ _ 1
1_ _ _ '
•_
_ _ I'_ _2_ _ 1_ _3
__
]1)36
May 27 •
-func 15" ....
-fUIlC 16 .
June 17.......... .
·June 17........... ..
.JulleI9..... __ . __. __
Junc2i.. __ __ .~
July2. __ ....... . July 16... • ...... .
July 18.......... __ ..
Jnly 24•• ____ • __ .
.Aug.1............. ..
AUI!.4.......... __ ...
INII1/I~~~ I.N~!~be:J Nli:~I!~:.I~v~I~~~~_i.~':'~I~~~:..~~~~~~:_ .~~~~~~.
~ I JI:::::: • •:-::1-: ::;::-:::;;~~;i:::!~ :~ ~: : !,
i
JlIC3."i'fj
"j' . _.......____ ...._________....__
3.05
.43
" .............. _
0
....
. .......... ______ •••• _•• ___ " . 0
.. _ ............... __ •. __ .••. , _.. __ ._ o
3 . . ..... ...
2.058
..
__ ..... , .. __ . _____._. __ ... ____ . 19.fT
Sept. I. . ______ . Sept. 2. ____ •.•.
Sept. 3. ___ .....
Sept. 7 " " " .
Sept.l1.._ ....
. . __
..
Sept.16____
0
.12
.35
.11
"1.
Sept.27......... ".
Oet.5 __ ...... __....
Oct. 7. __ ............,
Oct. 9 ____ ........ __ Oct. 10..............
~~t.~:.~==:::::::~::\
Nov. 13...... __ .. ·.1
No,'. 20""'''''' .... 1
Dec. 2.. ._. __ •___ ..
Dec. 6..... -Dec. 1:l....... __ ..__ ,
Dec. 20 ...... " . . . __ Dec. 2:~. _.. _~".., __ ~ ..,. .. _;
--------I
.08
I
6: l~ i
~.GQ I
.11 t
o '
~. 461
I.OS
I
:~r I
1.08
. ;2
0
S
05:1
0
(]
0
"
45
0
2\1
2-1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3
0
I
.90/
.37
0
0
0
3
0
S
11
80
Uti
0
[)
s
-'if
1
Q
6
1
8~ I
3j
31
Ii
2·1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
"
0
0
0
4
0
0
0
0
0
0
01
I
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
·- .. ·····ii·
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
()
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
------·0
0
0
0
0
0
0
16
0
0
0
As indicated in labk 5, in a concurrent test a heavy spore shower occurred in an
adjacent area where the disea~(' ,,'as abundant. These figures give some idea of
the relatively I5mall lIumber of SJlores disseminated in nature by wind-blown rain
as against that attributable in the main to min splash.
WIND
Cultural observations have sho\\'n that the matrix binding the spores together
dissolves at first rather quickly in water. The viscidity of the matrix increases in
time, and hard spore masses have been obtaincd by desiccation of the matrix in
culture. Much of the same change in the physical nature of the matrix would take
place naturally through l he drying influence of exceptionally high temperatures
and in the absence of rain. The month of .June 1936 was one of the driest and
warmest on record in Louisiana. The spores caught on June 17 (table 5) were
deposited as a group of fivc. Under exceptional meteorological conditions it
appears that spores may be broken off ill groups as dry fragments of a larger spore
.mass and transported elsewhere by air curr('nts. In this case, the action of wind
is indirect in that the dislodging of the aggregation of spores probably resulted
from the rubbing of the surface of the spore mass against neighboring needles or
stems of grasseS.
No dispersal of individual spores by the action of wind alone was found. Table
5, columns 4 to 9, shows the number of conidia prorated to the square inch of slide
area 011 123 slides that were exposed vertically in consecutive sets of 0 or 6, from
20
TECHNICAL BULLETIN 870, U. S. DEPT. OF AGRICULTURE
September 1, 1937, to January 1. 1938. No spores were seen Oil slides that were
exposed during 5 rainless periods. Conidia were deposited only during those peri­
ods ",l}en it rained and were found mainly on the 21 slides that were exposed a foot
above ground. Four spores (prorated to 16 in the table) trapped on 1 slide at a
height of {j feet may have been deposited by a wind-borne splash drop.
TEMPERATunE
Although little inoculum was deposited on slides during the first part of Novem­
ber 1937, brown spot spores were disseminated abundantly between Kovember
20 and December 2, The absolute runge in daily temperatures for the latter
period was 22° to 67° F. (-5.56° to 20.56° C,). It ReClUS probable that a crop of
.;pores matured during the relatively warm weather pre\'ailing in the first half of
N ()\ ember. A light rain on November 27, when the maximum temperature was
67°, disscminated this ino.culum.
Tempcrature has no direct effect 011 conidial dissemination. A combination of
high temperatures and low humidities, when sustained, will probably desiccate
the sticky matrix in which the spores are bound, so that rain will fail to dislodge
conidia from their place of production on pine needles.
DISCUSSION
Conidin, Or the brown spot fungns Ill'C produced Itt nll scnSOJlS of the
YClll'. nnd n.hllnduut disseminl1tion is known to h!lYe occurred in Janu­
;lTy,r.Iny, June, OctoUrl', Noyembcr, ilnd Decembpl'. By fill' most of
the disseminntion oceuI'S through ruin splilsh, nlthough wind-borne
rain splash n.ppen.l'S rcsponsihle for somc of it.
Y crr(tll (37) gn.thrl'cd datu on dissemination of the fungus from the
middle of JHJl.U1UT to JUlll' 30, J.933; the ·writer's observn.tions were
mndr in In.ter yen.rs and eovcTed, in the main, the lWl'iod from th(' mid­
dle of Junr to' the first of Jnnum·y. Yerrall obsClTed thnt conidia were
disseminatcd nJmndltntly on tlu'cc occnsions in 193:3 -·in Jilnufiry, )"[n,y,
und JunE'. His belief thnt l'e1n,livcly WH.rm tcmpern.tmes were llcces­
Sllry for much spore dischlll,gt~ WUS Dot bOl'ne out by the ,,'riler's
studics. llelativcly low tcmp(ll'il tures (50 0 to 070 Ii.) did not inhibit
disscminn.tion, proYidcd thl' SPOrt'S had mntured before the advent of
('001 wen.thcr.
The writer's demOllSLl'tl.tioll of the exist(,llce of the flscigcl'oUS stage
(lftheln'ownspotfungnsisofintcrest in connection ,yitit vill'iollS pltcnom­
pnn noted ill respect 10 disscmblfl.Uoll of the disCflSC iJl 11l1tnl'l' (29).
With rdercllcc to 11e('dlc infections, the hnr spot typC' of lesioll, often
obsence! mHny fcpt aboy!? ground on folirtge of tnll sltplings und mature
tre(\s. hns been eOJ')'('ctly illtCl'pretrd ns (Tic\ellc(' that spores of the
fungus W<'I'(, wind-dissel1lillatt'd to 80mc t'xicnt. K 0 cyidrllCr, ho\\,­
l'Yl'l', lIns herll gl1tlicl'Nl to ill(!icn.te thn.t disst'minl1tioll of individufLl
('onidifl occurs through the ngency of wind nlolle. Observation of
('onidill in 11<[ lIeous snspellsiollS in the In.bol'itiory hilS shown thn t they
tE'nc/ to lldhel'c to glass surfaccs when welt and thn t mere contact wit]J
\\'(1.1.('1' will not 100St'1l tlIc'm once tht'y hl1\"P dried 011 n. slide.
The
H ' lln('ity with which thE'se conklin. resist l'emoynl from n glnss 8m'fart' is
~tl'ikingl.y similar to thr hehuyiol' of spores of ('ocC07n?/Ce8 hiJ:.mali.<;, flS
l'l'porled hyKeitt ct nl (19).
Conidia of the' brown spot fungus fLPPfLrently fLl'C noL disseminnted
hy [J ir ClUTents Hnd('I' culturnl COJl(litiotls. :Spores formed Oll the
slll'fllCe of a brown spot eolony rCl11ilin indrfinitely in tht, matrix when
the slll'l'ncr of the cultllr(, is dry'. COl1idinl R])Ore hornR, dcsicClllcd ill
('uhur£', 1'l'llwin inLiwt fot' hours wlli'lJ pln('('d illWlltl'J'.
BROWN SPOT NEEDJJE BLIGHT OF PINE SEEDLINGS
21
From the results of many studies dealing with the mode of dis­
semination of Ascomycetes, the most plausible explanation for the
bar spot lesions on the overwintered foliage of tall trees is that they are
the result of ascosporic infections. The ascospores of the brown spot
fungus are forcibly ejected from their plnce of production on dead
needles and borne by wind to other needle surfaces located at various
distances above the ground. The bar spots thl1t appenr on the folinge
of young seedlings in early fall are thought to originate from conidial
infections, ns ascospores have never been obtained from blighted long­
leaf needles at that period of the year.
Bar spot lesions on the folinge of tall trees are evidence that spores
of the brown spot fungus are wind-disseminated, yet just us good
evidence will bc presented to indicate that the sensonal dissemination
may at times be limited to relatively short distances, even where dense
mnsses of susceptible foliage make conditions ideal for the mpid spread
of tllU fungus. The conflict in evidence may be reconciled if the
nscospores are considered air-borne and the conidia IlS disseminated by
water, with the mode of dissemination of ench of the two kinds of
spores sharply limited to these agencies, respectively. It is assumed,
largely by analogy from the results of more cri tical studies, that the
quantity of ascosporic inoculum is relatively limited, that it varies
greatly from year to year in tbe same locality, and that ascospores arc
disseminn.ted only during a, short period late in winter and in spring.
Ascocarps of the brown spot fungus appear on lirst-season foliage only
after death of most of the needle. Viable ascospores have been ob­
tained from ascocarps on longleaf pine needles collected in January,
February. and April, and mature" ascospores have been deposited in
April on g"lSS slides exposed in the open, several feet above ground.
The localized character of dissemination of brown spot conidia was
noted in certninnlll'series, in contrast with evidence in nature of direct
dispersal of ascospores of the fungus by air Clll'rents. A number of
parallel nursery beds, 4 feet wide and 138 feet long, were separated by
footpaths and SOWll solidly to longleaf pine in 1928 at the Texas Stat.e
Nursery, at Kirbyville. The needle diseuse first attacked the foliage
of sC'edlings in 2 beds at one' end of the nursery. By the following
winter the quanti.ty of the infected foliage WIts greatest in beds where
the disease had flrst appefll'ecl and leust in the last longleaf pine bed,
10 beds u,way. PrncLienlly all foliuge in beds at one end was badly
blighted, while infection wus very light at the other side, appro~:i­
mu,tcly GO feet away. Similnriy,!L progressive decrease in intensity of
the disense f!"Om the point where the Jenf spotting first started to the
other end of the same beel wus noted in a nursery in an adjoining State.
'VIlen fnctors inhibit the devclopmen t of ascospores in a given arel1,
dispersl1l ofbrown spot spores from original centers of eouidinl infection
to healthy, susceptible foliage would be limited to rain-splash distances.
Therefore, most of the seedlings in 1111 originally clean stand might,
escape serious defoliations for several consecutive sensons and begin
enrly active height growth.
This seems to have been the early history of the brown spot diseuse
on the foliage of longleaf pine seedlings in Ohapman Forest, near·
Uranin, La. Dense natural reproduction of lonp;lenf pine had become
established in this loenlity by means of controlled burning on 1,200
acres prior to the seed f1111 in October 1928. In the next five seasons
iufection on the foliage gradually incrCllsed distributlonally within the,
'.
22
TECHNICAL BULLETIN 870, U. S. DEPT. OF' AGRICULTURE
stand, but as late as November 1933 it had not become quantitatively
serious. As a result, the thriftiest seedlings started growth in height.
Later, the disease increased in intensity and much outright killing of
the foliage down to the needle fascicle was noted in visits in 1936, 1938,
and 1939 (pI. 2, A). Many dominant and once thrifty saplings were
almost defoliated by the discase to a height of 6 to 8 feet above ground.
Those who lllwe worked with brown spot disease agree that the
great majority of longleaf pine seedlings have no strong' inherent
resistance to infection. Presumably inherent susceptibility is con­
stant, and the foliuge of the seedlings in Ohapman Forest was as
susceptible to infection in 11.)29 as that of the seedling-sapling stand in
1939. That most of the sl'Nliings escaped serious defoliation from
1929 to 1933 is attributable Lo pOOl' conditions for spore production,
dissemination, or iufectioll rather tluw to iLny drect of the siLe on the
diseuse process.
Ohapman Forest is iLU <lislulICl" of 10ngleuJ pine ncar the northern
limits of the l1iLturalmllgc of the speeies, surrounded by a Im'ger stand
of loblolly and shortlcar pine in mixture. No large area of longleaf
pine is closer than 2 miles Lo the forest. This natural isolatioll strip,
composed of pines with l"elaLivply diseuse-rcsisL:lIl.t foliugc, may have
served to SCl'oen the seedlings in ChiLpll1iLl1 }i'orest from the ncnrest
abundaut source of nScospOl"es.
This is not an isolu,tod exal1lplo of diseuso escn,pe occurring dUl'ing
the most critic!ll period ill Lho life of seedling stands on unburned
arcus. In v\ushingLoll Pm'ish, L!l., most of a lot of nursery-grown
longleaf seedlings ill a small plantation that wus established in the
winter of 1923-24 ('sc!lpecl serious ,brown spot c1e.I'oliation, and many
of the plants sturtNI vigorolls height growth in their third seaSOll in
the field.
Disseminn,Lion of conidifL from their place of production on infected
needles to he!llthy folinge by the ngency of man or animals probably
oeems, although eyidence of this type of dissemination is lacking.
Probably much illfpct.iye material has been man-disseminfLted through
the rouLine llf1ndling of pine seedlings in nurseries. 'rransfer of
conidia by liYt'stock as they wander among infected see(Uiugs may be
of common OCCUITencc', pfll'Licularly during rainy periods. The slow
rate of sp1'l'ud of the diseusc through the seedling stand inOhapman
Forest is atll'ihutedp!lrtly to thcdact that grazing was not permitted;
tb(,l'dol'l" dissl'l1ullalion of SPOI'('S by livestock did not occur.
INFLUENCE OJ" Til E DISEASE ON SEEDLING GROWTH AND
Sl:RVIVAL OF l~ONGLEAF PINE
Oon trol of brown spo t diseuse was prcreq uisite to a COITeet appraisal of
the cfl'ect of defoliation on rate of seedling growth. Spray treatments
continued for 9 yeul'S and 10 months. DifferQUccs in height between
the spruyed hPltlthy s(,Nllings and the untreated disensed controls have.
furnished a busis for eyall11lting the dwarfing effect of the disease.
A number of different fungicides were used in order to obtain one
that would control the disease without causing chemical stimulation.
That the hvomblt' efred of treatments wns due to disense control
without the eom plieation of chemical stimulation was indicated by
similar growth response with different fungicides. Essentially the
same response occurred whether bordeu.ux mixture, lime-sulfur, eol­
G.-Average annual height. grawth of 1 ,3921Jlanled longleaf pine seedlin,7s rlass£fied according 10 height class
mId perceniage of diseased foliage, over Ihe period 1931-89
TADLE
Ilclt,lht clnss at tim~ of SlJel"t'fiSI\'C nnnllulmcnsurcmcnts
I
Percentnge of disenscd
folia~e
2U-4 inches
.
I'_~U-6_inclws,
OU-S inches :SU-IO Inclll'S; IOU-12 inclll's'12U-14 inches' HU-1I1 illCIll'SI6U-18 inches 18U-2O Inchcs 2OU-22lnebes 22U-24lnebes
_ _1
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In. No.
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l'to.
No. In. No. In. No. In. No. In. No.
111.
j\'O.\ In. ! No. 'I In.
25. 6
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2_________________________ • 425
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725 11.8
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22.2 I 67
25.0
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L ______ ._. _________ ._._._.
10______ • ___ • ________ ._. __ .
15 ______ • _____ ._. __ •. ______
20 ___ -.-____... ___ . ___ .____
25 ______________ ... _.______
30. _________ • ___ ... ________
35. ______________ •• _. _____ •
40 ______________ ..__ ._. ___ •
45.. _______________ •. _._. __
50 _______ .. _____ ._ ....__ ._.
55_________________________
60 ___________ .. _____________
6.1_________________________
70 ____• _____________ .______
7v ______________________ ._.
80..__ • _______ ..________ ...
tlS ________.________________
90 ________________________ •
95 nnd over___________ . ___ .
1
:1I
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33
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53
54
72
63
62
48
39
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.5
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17
S.4
9
0.7
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1.7
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26
2.4
162.3
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1.0
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2.6
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9
1.6
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1.6
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1.6
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3.7
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a.81
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'24:0-'. ::: r:::::,'---2"1'"- i7:0
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__ , :::::\:::::::\ .... 1<\ .. "2:3
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Based on 1 season's ~rowth after the estimates of tho llisensed Coliage hnd been made in winler.
~
~
24
TECHNICAL BULLETIN 870, U. S. DEPT. OF AGRICULTURE
loidul sulfur, 01' plain hydrated lime was used as a spray. Further­
more, soil treatments with powdered hydrated lime, the component
common to three of the sprays, failed to induce rapid height growth
among stunted seedlings. That the favorable response to the
treatments was due to disease control without chemical stimulation
was indicated also by tests to determine the minimum number of
sprayings needed to insure 1], satisfactory sapling stand; compare the
development of ll-year-old trees that had been sprayed 66 times in
6 years with that of 9-yeltl'-01d saplings treated only 11 times in 5 years
(pI. Z, B and C).
The experimental areas under observation, consisting of six
plantations and a stand of dense natural reproduction, were com­
pletely protected from fire. The growth data in table 6 were based
on successive annual measurements of heights of seedlings in four of
these plantations in LOllisinna. An a1111ual estimate of the extent of
infected foliage also was made for each planted seecUing.
A mther simple and rapid method for estimating the extent of defoli­
ation caused by the diseuse was devised in the study of the effect of
single fires on the needle blight. It consisted of making quantitative
estimates in winter of the leaf tissue lost on account of the disease
during the previous growing season. The estimates were made in per­
centages expressing the ratio of the persisting diseased needles, as well
as the dead (ab~cissed) tissue of the previous season's growth, to the
totolfoliage formed by the phLIlt during that season. In the absence of
abnormal defoliating influences, longleaf pine seedlings retain needles
of a given season on the average for 18 months. Needle shedditl!!,
however, normally occurring in fall, involves only those leaves that
huye passed thl'ough the second growing season. Foliage persisting
in winter on a seedling in the grass stage was formed during the pre­
ceding spring and smnmer. By making disease estimates in winter,
"second-season" needles were automatically eliminated from con­
sideration. Quick ocular estimnccs of this type made it possible to
examine hundreds of seedlings in a few hours. 1'0 determine the
avemge value for the disease in a giyen plot 01' stand, the tally of the
number of seedlings in each percentage-infection class was multiplied
by their class value. The sum of the products was divided by the
total number estimated to obtn,in the weighted-average percentage
of infection on seedlings in the given area.
In the following discussion the effect of the loss of functioning foliage
on I'll te of growth is considered .first with respect to heig'ht growth of
stands of seedlings and, in a second study, with respect to the average
annual height growth of plllnted seedlings classified by 2-inch height
classes.
.
EFFECT ON THE GnoWTH RATE OF STANDS
NATURAL REP.RODUCTION
In 1928, initial spray treatments of pine seedlings were begun cooperatively by
the United States ]<'orest Service and the Bureall of Plant Industry in an area of
dense natural reproduction near Bogalusa, La. 16 In 1932 the writer (27) described
the experimental area and reported small differences in height in favor of the
sprayed set of seedlings for 1;l1e period 1928-30. The average hejght growth of
seedlil~gs in the same area is indicated in table 7 for the period August 1930 to Jan­
uary 1936.
"An illustration of some of the plots In the area In AprfI lQ31 was publlsbed In JQ35 (S5, pl. 6, B).
25
:BROWN SPOT N.EEDLE ,BLIGHll' .OF PINE SEEDLINGS
7.-Average height8 -ana ·height -growth of tagged longleaf pine Beedlings.in40
,.milacre plots in an area of dense:naturai'reproduction, Bogalusa,La., for the,period
August 19,30 to January 1936.
T.:ABLE
'Sprayed
Treatment and plot
Seedlings
in 1930
Average
height
of tagged
seedlinb'll
In 1930
Number
Inches
NO.1
Bordeaux
sprayed 7 seasons:
L ________________________
2_________________________
3_________________________
4_________________________
5_________________________
6_________________________
7__________________ ______
~
Lime·sulfur
sprayed 7 seasons: 8.________________________
9______________________ •__ 10________________________
11_________________________
Lime·sulfur
sprayed 6 seasons:
12_________________________
13_________________________
14_________________________
Colloidal sulfur sprayed 6sca­
sons:
15_________________________
16_________________________
17:________________________
18_________________________
19_________________________
20_________________________
Controls (not sprayed)
I
Average
growth in
height
Inches
1.81
1. 56
1.23
1.54
1.32
1.46
1.21
10.54
0.00
1.81
2.96
2.42
3.13
1.15
126
135
157
174
1.65
1.06
1.28
1. 78
39
73
78
43
100
112
141
164
19S
77
139
161
177
2.10
255
342
I
Seedlings
in 1930
Avera:;e
height
of tagged
seedlings
in 1930
Average
growth in
height
Number
Inches
Inches
79
III
132
155
185
206
319
1.99
1.36
1.27
1.54
1.30
1. 40
l.'14
1.57
.55
1.76
.89
.59
.70
.43
12.50
9.75
5.94
21.16
140
157
177
183
1. 76
1..38
1.28
1.20
1.91
1.25
3.02
1.70
2.22
51.38
26.46
21.35
S7
90
93
2.76
2.02
1.54
4.54
2.92
1.22
2.92
2.01
1. 98
2.47
1.61
1. 65
35.00
13.94
21. 23
8.98
6.03
5.S5
52
2.34
1.56
2.05
1.74
.89
1.20
1.41
1.28
4.35
2.73
.72
.93
77
SO
98
104
149
.77
.48
I 'Vithin the ditrerent treatments sprayed plots and controls are listed in the ordor "f increasing density,
not as they occur in the field.
In the 5 growing seasons that had elapsed since 1930, the appearance of. the
20 sprayed mil acre 17 plots had changed completely. .As the treatments con­
tinued year after year, the abundant foliage on seedlings in the sprayed areas
crowded out the grass. One of the indirect results of controlling the disease was
to reduce grass competition and thus eliminate much of the effect of .ground
cover on rate of seedling growth. Most of the seedlings responded to control
of the disease by starting vigorous hcight growth. In each plot several saplings
became dominants, and keen competition for light developed. Because the sup­
pressed seeCllings started to die, measurement of height of seedlings was discon­
tinued in the winter of 1935-36. Height growth among the sprayed seedlings
has been favored by control of the disease and consequent reduction of vegetatIve
competition. The detrimental effect of high stand density on height growth
continued throughout the period of the test. Pessin (21), studying the effects
of density and of ground covcr on the growth rate of longleaf pine seedlings in a
similar area ncarby, found that as stand density increased, the rate of growth
.in height of the seedlings during 3 growing seasons decreased both in the denuded
and in the grass plots.
In the series of sprayed plots the avcrage growth in height was greatest in the
three plots (table 7, plots 12, 15, and 13) having the lowest stand densities, and
the least growth was made in plot 7, where the density was highest. In the
control plots, however, the growth-density relation was less pronounced. A:l~
tho\lgh the least height growth occurred in the densest plot, the greatest growth
did not occur in the plot having the least number of seedlings. Explanation
forthis diffcrence has been given by Wahlenberg (38), who suggested that brown
spot disease retards an early expression of dominance by damaging 'the larger
seedlings more than the smaller ones. In dense, heavily inIected stands it often
happens that the disease is .more destructive on seedlings in which the ,foliage,
just'oyenoppiilgthe grass; has become exposed 'to infect.ion from all sides and
is,:Jeast destructive on foliage of seedlings hidden in the grass.
After 6 'years or more of continuous and effective protection of the foliage and
despite fairly uniform development of the mass of seedlings when the treatments
17An.arcaof43.56 square feet, comprising 0.001 of an acre.
26\
TECHNICAL 'BULLETIN '870,U.S. DEPT. OF AGRICULTURE
began, the average height growth per plot varied from 1.15 to 51.38 inches.
Such differences are typical when the variable being investigated (in this case,
height growth) is affected simultaneously hy several factors.
Under the experimental conditions it was not possible to evaluate" separately
the effects of vegetation and of disease on the growth rate of seedlings. The
results are of interest as illustrative of the influence of disease control on an
early expression of dominance and of the detrimental effect on height growth of
severe root competition due to abnormally dense stands of natural reproduction.
More intensive effort was given to a study of the growth of longleaf pine in
plantations, as the effect of the disease on early height growth is more clearly
demonstrated with planted stock than with stands of natural reproduction.
PLANTATIONS
Spray treatments to control brown spot were practiced for different periods on
six plantations: Four in Louisiana, one in Mississippi, and one in northwestern
Florida. The. early height growth of the seedlings in four will be considered
first with respect to the effect of the disease on the growth !;ate of the stand.
The seedlings used for planting were 1-year-old, uniformly graded nursery stock,
and, when planted; the foliage was almost disease-free.
PLANTATION NO. 1
In 1932 the writer (27) reported on the status of the early development of 378
sprayed and 164 nonsprayed longleaf pine seedlings, part of a commercial planta­
tion of the Great Southern.Lumber Co., in Washington Parish, .La. Spray treat­
ments had begun in April 1929, 4 months after establishment of the plantation.
In December 1937 the average height of the 331 surviving sprayed trees, at the
end of their ninth season in the field and the tenth from seed, was 13 feet 9
inches, in ,contrast with an average height of 8 inches for the 95 untreated seed­
lings still living. Plate 2, B, illustrates the status of sprayed and unsprayed parts
of the same plantation in February 1939. On this site height growth of the
unsprayed stand has already been delayed 10 years by the needle blight.
PLANTATION NO.2
In the winter of 193(}-31 the writer established a plantation about 2 miles. from
plantation No. 1. Of the 170 seedlings divided equally among 10 rows, 68 in the
second, fourth, sixth, and eighth rows were first sprayed in April 1931; the
eleventh and final treatment was applied in November 1935. Serving as controls
were 102 seedlings in the first, third, fifth, sevPl1.th, eleventh, and twelfth rows. IS
The average height of 54 surviving sprayed trees in October 1938, at the end of
the eighth season in the field, was 11 feet 2 inches, whereas that of 65 surviving
seedlings in the unsprayed rows was 1 foot 1 inch. At the beginning of the
ninth season in the field, 57 seedlings among the 65 controls were less 'than 2 feet
tall. The relative df'v210pment of sprayed and unsprayed trees in part of this
plantation is shown by plate 2, C.
PLANTATION NO. 3
By 1933 it had become evident that a relatively few spray treatments would
reduce the disease sufficiently to bring most of the seedlings in a plantation to
sapling size. In March 1934 plantation No. 3 was established in a clearing
adjoining plantation No.2, in order to demonstrate whether further reduction in
the number of spray treatments to the rotation would give adequate disease
control. The plantation was divided according to treatment into 3 lots of seed­
lings, all of which were sprayed 4 times the first year. Then seedlings in even­
numbered rows were sprayed only twice during the. second growing season.
Finally, only 7 of the 12 even-numbered rows were sprayed twice in 1936. The
comparison in growth in this case is not between heights of .treated and untreated
pines but in relative height development of 3 lots of sprayed seedlings, each dif­
fering with respect to the extent of defoliation that occurred, the number Of
growing seasons treated, and the number of treatments in the rotation.
In the winter of 1939-40, after 6 years in the field, the average height of 68
seedlings sprayed 8 times in 3 seasons was 4 feet 7.5 inches. The second group,
37 lleedlings sprayed 6 times in 2 seasons, averaged 3 feet .2 inches; and 102
seedlings, treated 4 times for 1 season only, averaged 1 foot 4 inches. The
nearest untreated seedlings were located 100 yards away in the older plantation,
18
Seedlings in the ninth .and tenth rows, given a different spray treatment, are not consldered!here.~
BROWN SPOT NEEDLE BLIGHT OF PINE SEEDLINGS
27
No.2. Obviously, these seedlings are not controls for those in the younger
demonstrational area, yet it is noteworthy that the 71 surviving diseased un­
treated seedlings in the older plantation had an average height of 5.3 inches at the
end of the sixth season.
PLANTATION NO. 4
In December 1934 a longleaf plantation was established in central Louisiana
by the United States Forest Service, to be used by the writer in demonstrating the
effect of the disease on seedling development. The first spray treatment was
made in November 1935 and the fifth and last in December 1937. After 4 vears
in the field, the average height of 485 sprayed seedlings was 9.4 inches in contrast
with a 4.6-inch average height for 315 seedlings in the unsprayed series.
A,> a group, the unsprayed seedlings in plantation No.4 were thriftier than the
unsprayed in the other plantations. "lean heights of the untreated in planta­
tions Nos. 1 and 2.were 1.8 and 2.0 inches, respectively, at the end of their fourth
season in the field. Estimates of the disease on the foliage of untreated seedlings
in plantation No.4, made annually in wint.er from 1935 to 1938, were 10, 18,26,
and 43 p?,rcent. The mildness of the di ease in 1935 and 1936 is reflected today
in the better development of the untreat.·'d seedlings in plantation No.4.
EFFECT OF DEFOLIATION ON THE AVERAGE ANNUAL HEIGHT GROWTH IN
VARIOUS HEIGHT CLASSES
Most of the annual height growth of thrifty longleaf pine seedlings takes place
early in the growing season, before there has been much development of sprinl!
foliage. The presumption is that this early growth is dependent on the quantity
of food accumulated during the previous season. TheBe considerations suggested
that the annual height growth could be correlated with the extent of the disease
present on the foliage of the previous growing season. Obsen-ations on the early
development of planted and sprayed seedlings led the writer to believe that vig­
orous height growth will not often start until the seedling, regardless of age, has
reached a height of at least 2X inches. Because of the minimum development
in size necessary before a seedling can begin active height growth, the growth data
in table 6 were based only on seedlings that were 274 inches or more in height.
Between 193] and 1939 successive annual height measurements and disease es­
timates were made on 1,392 different seedlings in the 4 sprayed plantations in
Louisiana. To treat these data statistically it ,,-as necessary to group the seed­
lings by 2-inch hei~ht classes.
The growth data presented were plotted according to the percentage of dis­
eased foliage, as shown in the first column of table 6, a separate curve being
drawn for each original height class. The individual curves were then har­
monized 19 to obtain the set of curves shown in figure 1. It will be noted from
table 6 that there ,,-ere not many observations except for the lowest infection
class or the lower height classes. The shape of the Clln'es for the other plasses
was largely determined by the shape of the curves based on stronger data, and
the relative height was determined mainly by the height of the 0 to 4 percent
infection class.
The curves indicate that complete defoliation greatly retards the annual height
growth of all seedlings, regardless of initial size. It will be noted that light de­
foliations (10 and 20 percent) cause more reduction in the growth rate of smaller
seedlings than of the larger. For example, the average annual height growth of
the seedlings in the 2X- to 4-inch height class, following a 20-percent defoliation,
as read from the curve, is 1.10 inches, which is one-fifth the average annual growth
in height of like seedlings in the lowest infection group. On the other hand,
the average annual height growth of the 22X- to 24-inch seedlings after 20 per­
cent defoliation is approximately 75 percent of that indicated for similar-sized
seedlings with relatively healthy needles.
OBSERVAT,IONS ON SURVIVAL OF SEEDLINGS IN PLANTATIONS
The effect of successive annual defoliations in retarding early growth in height
of longleaf pines has been demonstrated consistently in plantations and in natural
.reproduction. Death of seedlillgs, however, as a result of a gradual weakening
by premature defoliation, seldom a conspicuous phenomenon, may often go on
for years unnoticed. Observations indicate that at least three successive annual
defoliations are required to weaken a seedling sufficiently to kill it.
I'
Following the-method outlined by Chapman (t, pp. 168-174).
•. 1
28
-
TECHNICALBPLLETIN 870, U. S. DEPT. OF .AGRICULTURE
:25
:tn
IIJ
~.%
.0
-
,Z
-20
;.
%
~
0
.~
C)
15
~
%
:"
.IIJ %
10 ..J
4111[ ,';:) Z
·z
4111[
5
OL--L~-=~=±==~=t~~~~~±-~
o
10
20
30
40
50
60
70
80
90
100
DISEASED FOLIAGE (PERC.ENT )
·'
l.-R,elation between average annual height growth of planted longleaf
pine seedlings aud percentage of diseased foliage. Each curve represents the
seedlings in a given height class. Height growth is based on one season's
growth .after the estimates of the diseased foliage had be.en made. Numerals
on the curves indicate the height class in inches at the beginning Of a growing
season. The arrows indicate the end point of observational data.
FIGURE
Apart from the disease, several factors have adversely affected the survival of
longleaf pines in the four plantations employed in demonstrating the effect of defo­
liation on height growth of seedling stands. Ground cover competition and tram­
pling by cattle have been detrimental. Except for the spray treatments, man's in­
fluence has been unfavorable. Vigorously growing saplings were cut down because
they interfered with a telephone right-df-way. Once, laborers in clearing for a high­
way hauled stumps by tractor across five rows of seedlings in one plantation.
When the plants were small about 2 percent of the seedlings were defoliated.annu­
ally ~y leaf-chewing insect larvae. A burrowing rodent ('Geomys sp.) killed many
seedlings in plantation No.4 by destroying the taproots just below the ground
line.
The longer a stand of seedlings remains dwarfed by the disease the greater the
hazard that it will be depleted or wiped out by other v,dverse factors of the environ­
ment. In this manner needle blight contributes indirectly to low survival, though
other facto1'& may be the direct cause of death. In these circumstances, a tree-by­
tree. analysis of mortality, to determine how mu()h of the dying had been caused by
the disease, would not be justified.
.
.
BROWN SPOT NEEDLE BLIGHT OF PINE SEEDLINGS
.2~
In the following summary, mortality due to all causes is given in perceni;~",,·for
sprayed or nonsprayed groups of seedlings in each of the four plantationli. After 9
years in the field, 12 percent of the sprayed seedlings and 42 percent of the checks
in plantation No.1 (pI. 2, B) had dicd. In plantation No.2 (pI. 2, C), mortality was
20 percent {or the sprayed group and 36 {or the nonsprayed, 8 years after planting.
On the other hand, in plantation No.4, 37 percent of 994 sprayed seedlings had
died by the end of the fifth season, compared with a loss of 34 percent among 472 of
those not sprayed. In this case, the lower survival among the sprayed plants is
explained by differences between the plots in ground-cover competition and
damage inflicted by a root-eating rodent (Geomy.~ sp.) and the Texas leaf-cutting
ant (Alta texana Buckley). After 6 years in the field, mortality in plantation No.3
amounted to 11, 9, and 5 perccnt, respectively, among seedlings sprayed {or I,
2, or 3 seasons.
SOIL FERTILIZATION IN RELATION TO GROWTH OF DWARFED PINES Two milacre plots were laid out in August 1931 in a dense stand of
ll-year-old longleaf pines dwarfed by adverse growing conditions, in­
cluding annual defoliations co.used by the brown spot fungus. One plot
was sprayed SLX times until April 9,1932. Then spraying ceased, and
3.2 pounds of a 3-10-3 commercial fertilizer were scattered over the
plot at the rate of 3,400 pounds an acre. Seedlings in both plots were
thenmulcbed withdel1d gmss and pine straw. Tbesamefertil:izer treat­
ment was repeated in April 1934. Nlost of the effects of the treatments
on beight growth of the seedlings is credited to the soil fertilizations,
because the spraying was continued Ior less than one growing season
and because a similar growth response followed fertilization of
unsprayed, unmulched seedlings.
The averuge height of 64 fertilized und 34 unfertilized seedlings was
1.0 and 0.9 inch, respectively, in Januury 1933. The initial develop­
ment of the two groups wus therefore very similnr. The average height
growth by Febt'uat'Y 1939 wus 5.5 inches for the fertilized lot and 1.0
inch for the unfertilized. The average percentage of brown-spotted
foliage on the same fertilized seedlings was 44 in January 1934 and 27
in February 1939, compared with disease estimates of 54 und 60 per­
cent on the unfertilized plants.
The capacity of the seedlings to elaborate their food reserves had
been balanced for :yeurs by the nunual destruction of the foliuge by. the
fungus. The seedlings were kept below the minimum general develop­
ment (38) that longleuf pine requires for initiating rapid height
growth. The fertilizations upset this balunced condition possibly by
increasing the photosynthetic efficiency of the uninfected foliage.
The eadiest expression of dominance in the fertilized plot was noted
after the growing senSOll of 1933, when one seedling attained a height
of 4 inches. By January 1934, 30 percent of the foliage of 1933 on this
"dominant" seedling had been killed by the disease. Despite this
severe infection, the seedling continued to grow und became the domi­
nant sapling in the plot.
Height growth, in spite of severe attacks on the rolinge, occurs when
the difference between two antithetic processes favors the plant.
Height growth resulting Il'om soil fertilizntioll demonstrates the ca­
pacityof a seedling to overcome or otttgrow the diseased condition.
On the other hand, resistance to brown spot infection-evident when
seedlings never become seriously diseased, nlthough the inoculum
may be present on the foliage yenr nfter year-is autogenous. When
the disease is allowed to go unchecked in nurseries for long periods
30
TECHNICAL BULLETIN 870, U. S. DEPT. OF AGRICULTURE
a very few seedlings never become badly browl1-spo~ted although
surrounded on all sides by badly infected foliage. Superior gl'Owth,
increased vigor, and relative fr('edom from diseuse distinguish these
individuals as belonging to discas(l-resistunt biotypes. "While the
capacity of seedlings to pL'Oduce resin has been connected with their
resistance to brown spot infeetion, it is pl'Obuble that other factors
also e':\'-1st. Susceptibility to inf(>ctiOIl dol's not dl'IWnd on vigor of
the seedling. The bro\\;n spot fungus oflf'll attacks the Joli~gl' of
vigorous s('f'{llings nlld (,:lUS(,S 01(' same degl'l)(, of defoliation as on
1£'ss vjgorous plants. Severe defoliaLions of vigorolls longlell[ pine
seedlings and Sl1.plillgs IIfI:vp or('uI'l'NI ]'PllI'ltLpdl,Y in t1H' Cbapman
Forest, nelll' Ul'fillin, Ln." in ~lississippi, [lnd in Flol'idn.
l{VI"ECT OF Sl:\GLE l,'lItES 0:\ TnE DISEASE
Extensiv(' sllrv('.\'S in th(' Ionglf'[l[ n'gion, l'lIlhrncing all area from
Texas to South Curolintl., w(,re begull in J o:n to dpterllline till' effect
of a given fire on Ul(' <list-nsc !lnd the clu\·[.Uon of the effect. This
phnsc of tlit' inycstiglllion wns continuNl on n. rt'~.donfll bnsis n,nnun.lly
for the next 5 )'(·H/'S. In thes(' SlU'V('YS, obsrnmtions wrl'(' madC' OIl
the sanitary ef[pct of Il. Ilumbrr of fil'(\S o('('ul'l'ing prl'viously in the
sanH' gellernl1oCl1Jity. 'rnbk 8 shows the typ(' of dn.t[1 ohtnined from
this study in Cl1,m(/rIJ County, Gn.. li'rom dl1.tn. collected from 1931
to 1933, the writer conclucted that it single fin' greatly reduces the dis­
ease for tIu' first scnson fmd oftcn to a lcss(,I' l'xU'llt for the' second,
Occasionally, becn.use of the silnitnry effed ofa singlp firc, there were
areas where Il. l'cduetion in till' disense wns stilll'vid('nt bv the wintcl'
of the third seaSOll,
..
TABl,};:
S.-The relation of thl' IJ/'own lipot 1!1'edlc blight Lo {he period elapsing since
fire, in a.loc(llity in sol(tilClIsl£'rn Oeorgin
Averago
\' rowing seasun sillr(' firc
Dutt\ Cjf exumination
Dntc Of fire
dCll.ll
needle
tissue
NowUlbt'r 193L ..... __ _
D(lC(!mb(!r W:!:L~~ ___ ~_~.~".
~.
~o\·mniJ\!r 193a _"_~ .... _~".".
SPrinJ; IU:lO .'" .... , ._ ..... 1\o\'clllhcr 10ai .......... .
..
...-
Sccolld ............. , ... _............... {fJ)l;::~fr;~uN3~··'·
lJ~~~~::H~:/Rj!k=::::
JUllUnr;·1931.:: ~ ""'::: .. :::::: Jo"'ebrunry JO.3O.......... .
Tbird ......... ___ ..
'''_j
SIll'lnJ;Hl30 ___ .•• __ . .
ll~ct'fnllt'r!932 ... _..... __ ..
• .......... Sprtn\: 1031
., ... _ __
1\0\'c1I1bor 19:13_____
,_,_"
{ FcbrunryJ9:l3 . . . _ .... _ Jl cbruIlryJ9:JO..... _... _.... _..
FourUlw_~~ .. ~_~ .• _.. ~"_~
;\lnrCh IU2S._ .. _.. , __ .
__ .. _.... ~ Spring W2"J. ____
{Spring W:1O .. __ .
_
_
__ '_
!
1\o\'~1I1b~rl!1:11 ._._ .... _._.
tll\(I(1l1Jber W32_ •. ~._~_~~~¥~~
Xo\,cmbcr 1033.... _.......... _.
._.1 nccemh~r
Percellt
1.4
1.7
.0
2.4 5,8 6,1
7.4 12.3
S.O
l4.2
8.3
16.5
12.2 pllIrch IUZS .. _ ... _. ____
1032 .. __ ••..•• _•••
Flrth ......................... _ ••. lsprint; HJ:!'J .• _ . __ . . "-I.· ::\o\'l'mbcr 1933...................
fo'cilrunr;' 193L................. 1 j<'cbrullrl' 1936 ..................
22.7
13.1
30.0
IU2S ... -•• -. __ --_· .. _1 No\·ember 1033...................
·•·····.. ···.. ··.... ···.....·...... l{"tu~ch
t ll ]Jrl11J; 1!I30_
... _....... _·_ .... 1 Fcbrullry 1931)__................
39.0
Sixth
2~.0 As the intensity of grnss fin's yarics greatly with scverill factors,
the sanitary effect of different fircs would \)l' expected to vary, Re­
peated Ulllllllll CXamiJJlltion of the same burued arell. was the indicated
procedure, although not always possible. A more critical study of
31
BROWN SPOT NEEDLE BLIGHT OF PINE SEEDLINGS
the effect of a single fire 011 the disoase was undertaken in a dense
I3-year-old stand of Ilfltural longleaf pillC reproduction llcar Boga­
lusa, La. On February lG, 1934, fire pnss('d 0\7cr 45 anrcs of this
stand which hnd bcc'J) burncd on :iVlarch 21, 1.928, in an 800-acre fire.
Seedling counts in Oetober 1934, hnsNl on 82 smitH sample plots
within thc area of the smnHer firr, indicat('d an n'"el'uge stand density
of 10,000 to thc nere. At tli(' til1l(, of the s('cond fire the great majority
of the seedlings,hnd not stul"ic'd ,"igorous lJ('ight gl"O"oLh. Rdativcl:r
few of th(' sN'cllrngs hnd ([('veloped into sttplitlgs.
Around tlll' nOlthern, pnstt'l"I1, nnd \"('stl'l'n llllll'gins of this fU'ea
therp was un almost unbrokl'll <I('ns(' Stilll<l of h('moil.,- infcet('d srecllings.
Thcse, then unburlled for six gro"oing f>l'HSOIIS, 8('l'v('d as the nCltl'cst
soun'p of ('xterl1:l1 iJlo('ulum.
Littl(' inff'ctin' IlHl.tl't'inl WllS [('ft within till' hUI'ned tHCit. All
folingr noted had lJe'en ('OIlSIIJ1l('d up (0 :! f('d nbo\"(' the ground and
down to n.n inch or two of tlw 1I('('dl(' Jasti('l('s. All foliage flbove the
zon(' of comp1ett' combustion W:lS eompll'lply or partly seorched up to
8 feet above th!' ground, and in plnces the folinge on some of the tnJlest
saplings wus eomplptdy scordwd to Iii f('Pt. TIl<' few brown spot
lesions to survive within the' bUl"llNL an'n wcon' bur spots on the foliage
aboyl' tll(' ZOI1(' of seol"('l1 i ng ht'at. Fru it bodips of the brown spot
fungus form ollly YPIT I"IlI"C'ly from bnr spot lesions, and temperatures
that kill lwpdJe tissu(' nlso kill the browll spot fungus in thnt tissue
(36,37).
Eight transe('ts W('I'(' run pnrnlh'l to nnd nt (\t>finite intrrvals from
the unburned mnrgin nnd nwrked for future r('[('rcIWt:'. Til(, loeation
of these transects with n'sIwc!'. to thl' Illl1rgill is indieatpd ill f1guJ"e 2.
The figure's ill tl1l' p('re(~nf:nge ('olumns of lahl(' 9 ttre till' ('stimnt('s of
the discuse, bused 011 not I('ss thall GO nor morc thtUl 114 s('('dlings
selected at mndom for eneh 10('ntiOll. Trnnseets 1 tlnd 5 were never
more than 47 or GG f('ct, I'('spectively, from thl' llCflrest ('xtel'l1al
source of inoculum.
TABLE
9.-Seasonal .~pread of brown spot needle blight after a. single fire,! related to
distance from nearest Lox/ernal source of inoculum
Diseased, foliage
Scason;f~ter fire 1 - - - - - - - - - , - - - - - - - - - - East side
West side
I
Date examined
Mar. 21,
_______
f_(_CO_ll~_~_OI_) (Il~~;;~d)
Control
1 '2
---~l pct.j-;;;
3
I
I
r----;'-'--I
.j
(colJtroll 5
I I
6
7
8
pCl·1 Pel. Pct.
"IIprt"l~!~!
5
431 9 6 i
5
2!
4~
37 i 3,! I 32
34
43
46
45. ·In 1_____ .___ _
pct.!
December 193·L______
7
1
:18"
7
7
December 1IJ35___ '_' __ 1
8 'I
2
38 I 30
3~
3~
Februnry 19:1'- __ .____
0
:l
451 4-! ·1, I 48
January JU3S__ ' _______
10
.J
·15
-._1
1
I Co\"criug ,15 acres within au Soo·acre area thnt burned oulllareh 21,
"
Burned transect No.
Durned transect No.
Feb. 10,
j
451
44; _._:
j
...... __
48
1925.
In Decembcr 1934 the cxtent of the discuse on the folinge of seed­
lings along these transects wus n,pproximntcly one-fif 1, of tlmL found
in the control m·eas. Seedlings along tmnSl'cts 4 and 8, located 600
and 300 feet, respectively, from the east and west margins, showed
one-seventh and one-eighth of the diseuse in the control areas at the
same time. A year later, the extent of the disease on seedlings along
transects 4 and 8 was approximately three-fourths of that on seedlings
.,.
""A"
32n:CHNICAL ,BULLETIN 8.70,U. S..DEPT. OFAGRICULT.URE,
o
'N
100 100100400
.SCALE· IN FEET
4
3
TRANSECT NO,
PLOWED FIRE LINE
-------._---...,--- ...... _------------2.-Sketch of a 45-acrc area burned February 16, 1934. Estimates of
the brown spot disease were made annually on seedlings selected at random
along transects run approximately at right angles to the direction of the nearest
external source of inoculum.
FIGURE
'
in the 8-year "rDugh." The single fue greatly reduced the dis.ease
for the first seaSDn and tD a much lesser extent fDr the secDnd. The •
slight differences in disease within and without the burned area nDted
in later years are thDught tD have nD direct cDnnection with the fire
.of February 16, 1934.
:AlthDugh fire had destrDyed mDst .of the infective material .over 45
acres, dense stands .of brDwn-spDtted seedlings bearing much dead
'fDliage harbDring the ascigerDus stage .of the fungus surr.ounded the
burned area. FrDm this external soUl'ce of air-borne spores en.ough
.in.oculum tD cause general infectiDn .of the new needles within the
"burn" came 8 weeks after the fire. Cattle attracted t.o the area by
the new .gr.owth .of grass undDubtedly assisted later in the tranSfer .of
conidiafrDm their place DfprDductiDn on infected needles tD healthy
i.oliage. In this instance, duratiDn .of the sanitary effect .of the fire
,was'essentially limit.ed to the first gr.ow~gseas.on. Relatively.rapid
spread,hDwever, .of the needle blight f.ollowing single fires .has .l.ong
:been .observed in .other localities, prDvided the area burned DY.erwas
·surrounded by larger areas l>eoring dense stands .of infected seedlings.
BROWN SPOT NEEDLE BL1GHT OF PINE SEEDLINGS
}~UNGICIDAL
33
CONTROL
NURSERIES
There are few diseases of seedling conifers more amenable to control
under nursery conditions than brown spot needle blight, Once
nursery infection has started, however, the presence of dense masses
of susceptible folinge produces a condition highly favo1'l1ble to its
spread, ]Tungicidal control wns begun in 1928 with experimental
field plots, established to determine the eil'cct of the diseuse on early
growth, Spruy control, successful from the beginning, wns soon
undertakcn at severnl southern l1msel'ies and is now routine pl'llctice
in Forest Service nurseries C'ngngcd in quantity production Gf longleaf
pine seedlings, 'Without this control the genomi distribution of the
disense in the southern pine l'l'gion would ll1flke Inrge-scalc production
of clean plan ling sLock impossible,
Bordenux mixture, lime-sulfur, colloiclnl-sulfUl', calcium-caseinate,
or zinc-lime sprays wcn' usC'd for seycrul years in field-plot tests,
Bordeaux mixtul'c pl'o\'cd to be tbe best from the standpoint of ef­
fectiYclless and noninj uriousness, It WIlS prepnred at the rate of 4
pounds of copper sulfate and 4 pounds of hydrated lime in 50 gallons
of watel', '1'0 this wns Ildded either cnsein spreader (calcium cnse­
inate) or 'whale-oil soap at the rate of 2 pounds to 50 gallons of sp1'l1y
solution, Rn,w linseed oil nlso wns used experimentally with bor­
deaux at the i'ntt' of 1 quart to 10 gnllolls of solution, Santomerse S
(snIt of 11 substituted fu:omnLic sulfonic ncid ill nqueous solution),
mixed at the rate of 1 pint 1.0 100 gnllons of bonlel1,ux mixture, also has
given favorable results in Forest SelTiee nurseries,
Four gallons of the spray will covel' about 1,000 sqllarC' f('et, At
this I'ate nn acre in solid nursery beds would require 175 gnllons of the
fungicide, Three or four applications of bOl'denux mixturc during a
growing senson ma~r be expected to gi\'e good but not necessarily
complete control. Since conidia of the brown spot fungus are dis­
seminated by the splnshing of min, the frequency of spray treatments
should be increased during sensons of unusually miuy wCllther, In
!}prayillg longlen.f seedlings in Gulf States llul'seri('s it is advisnble to
begin the trentment nbout the lust of May and 1inish in October or
November, Because sporulation nnd dissemination of the fungus
also occur in wiuter, seedlings that nrc held in the nursOl'y during this
period should be spmyed,
PLANTATIONS
Although the spl'nying of phmt.l1tions mlly nol seem C'conomicuUy
feasible, refol'cstu,tion with longleaf pine will be ncili('v('d mol'l~ quickly
by a combination ll'Clttment involving site Pl'l'plLl'(l,tion !lnd spl'l1.ying,
than by replanting the S!ln1l' uren lwo 01' three timps, 'l'hp ('ost of s(~ed­
ling replacement mil}' well ('x('N'd til(' ('ost of site pr('pm'n.tion and fun­
gicidnl con trol.
Pessin (21) hus shown thn,t g[,ound eoY('[' hns n d<,tl'inH'lltnl ('fl'l'ct OIl
the rate of growth in height of 12-yenr-old longh·ttf pitH' s('('(llings in
plots laid out in tHtturall'cpl'oduetiol1, It is eOlw('ivn.blC' lIUtt the UIl­
favorllblc ell'eds of ground COVel' wuuld. be eyen mol'(; pl'onOUtH:ed on
recently planted stock tluln on older seedlings, Some typP of si \:P Pl'('P­
aratioll on mnny cut-over longlenfpi},e 11I'eaS is obyiollsly neNlcd prior
to artificinll'efol'cstntion witll 1-0 seedlings, Bul'tling thl' planting site
a few weeks bcfol'chnnd would serve tht' following purposC's: (1) li'neil­
34
TECHNICAL BULLETIN 870, U. S. DEPT. OF AGRICULTURE
itate field work, and (2) destroy spores of the brown spot fungus on
any diseased seedlings present.
In Ill'cl1swhere browll.spotdisense iss(werc, planted seedlings would rc­
quil'etwo semiannual tl'en,LmcnLs with borden.uxmixture during each of
·th0 first two seasons in the field. FoUL' sprity trel1tments combined with
site prepn;r:ation as indicltLed would be ('xpeclNl to reduce the diseuse
sufficiently to induee n,ctivl' height growth among enough seedlings in
the pln.ntiLtioll to insure 11. sn,Lisfllctory slLplillg sttl.ll<l. The cost of the
sprn,ying, howl'yer, would increus(' the ('ost of n, plUIlLn,tioll [l,t lenst $4
an n,cre. Fungicidnl contl'o! foJ' IlI'l'US 0[' IlllLul'fLl longlconf pine 1'epl'O­
ducLion does Bot n.ppenr fensiblp.
"
THE DISEASE AND FOREST MANAGEMENT PRACTICES
The lil'(' prohlem on In,r~t' areas of fort'st land in the longlcaf pine
region is Iwing su(,(,pss[\lll), IlH't, In.rgely through Ute operfLtion of the
ClfLrke-1Jei'\nry In:w. Although the !,psuils of {il't~ protection have in
till' main proYNI bpnrfieinlto soutlwrn pine for('sls, n.Ltempts have not
bp(,11 unifoL'mlJ' su('c('s"ful lo 1'l~pl'oduee 10ngienJ pin(' ai'tificially or
nn,tural1y in nrens wh('1'(' fin' hn" be('n ('omplelely excluded 1'01' years.
l'n(lcr thp conditions impos('(l, the ('ady growth o[ seedlings hus been
slow nnd unsn,tisfll('lory. As olle result, 11, syslemn,tic progl'nm of re­
phntiug cut-oypr, un(\Pl'stoC'ked longleaf al'ens to Pin'lIs caribaea. hns
been under Wit)' in tht' Gull' Stn,Lps sinee 1935. Browll spot disease hus
plnypd tUlimporlnnt lHtrl in delerminillg fo!'('st planting poliey in the
longlcn.f pine region.
The slow lH'igh t growth of longleaf pine sepcUings during the fil'c;t
3 Lo [) yertL's nUt'!.' gprl11inn.tioll is pn'sumfl.hly an inhprent cllll.rneter. On
til(' other hnncl, the en,usPs for til(' stuntpd ('ondition of 95 percent of a
stn.nd of plnnled sC'('dlings n.ftpl' ] 0 yen,l's in the Hold Ilnd for thC' I1ltnism
of sttLnds or nn,tllrtll sepdlings 1'01' 15 and 20 yetlrs nn' Pl'cstlll1fLbly en­
yil'onnwnlnl .ill origin.
For SOI11(, lime, (ol'l'stprs huy(' 1·('('ogni7.('d tIlt' delrimenbll influence
or brown spot ll('l'dlp hlight on PHd)' growth of 10nglC'ILf pinp st'('(Uings
(3, 4, (8). '1'11(' ('{rpet of sU('('pssiw IUlllun.1 drfolil1tions dm' to the clis­
l'nse muy he so 1mlnn('NI against tilt' I!I'owth ('n,pneity or the sC'edUngs
tb!tt the majority will still 1)(' in tll(' s(,Nlling stnge !tHor] 0 yeal'S in the
field. '1'h(' p{r('et of ddolintiolls (,tllIlwd \)1' nnnu:rl wint(,I' fin's has like­
wise he('n rN'ognizl'd tiS tlell'im('nlal to" (,tll'l? gl·owlh. ,!'-nhlen\)el'g,
Gl'('('~l(', ancl }{('('d (3,cn )'t'jlo\'l(·d lhnlnllllunl cldolintions by fin' nnd by •
brown spot. dis('lIt'l' 11l'l'\"('1\t<,<1 SII('C't'ss[ul l'PgPIlPl'l1.lion of longll'fL[
pines I1t }.1(':\ eill, ). fit's., [01' n,t h'ilt'l 12 )"<,11l'S. Theil' eont'l usioll tlw,t
slLccessful rpg('IH'I'll1ioll of LIlt, s]wei('s wht '1'(' browllspol discnse is se­
veTC dCP(,Il(l::; on S{)Il1t' s,rs[(,lIl of lwrioclie ('onll'oU('(l btll'lling ('onfiJ'llls
Ohapml1,Il'S ohservatiolls [rom pxppl'impulal work n,l l\'ilnin" La. (3).
'1'he brown spot disPtlS(, and Y('gl'ln,{jy(' competition, whieh on tlrcns
long unburn('d ineludps lll<' slllolhpring :lnd oyprtopping of sced1ings
by vegetn.lncCUl1HlltLtions, botb contribute to the dwn,rfing of 10ngle11.f
pine reproduction. Both Clwironm('nlnl conclitiollS I1I'C ensily amend­
able through proper liSP of fire. ,'-hell tL single ground fire pusses
through a stand of infectpd se('dlillgs in winter thc rnnss of inoculum
is destroyed and-the exLent of the discnse during the foUowing season
is invariably greatly reduced. This reduction permits retention of the
needles through the second senson, which appnrently furnishes the
stimulus for vigorous height growth. The earliest sel1sonal height
growth antedates the development of spring foliage. This growth
BROWN SPOT NEEDLE BLIGHT OF PINE SEEDIJINGS
35
doubtless depends on the capucity of tbe seedling to elaborate reserve
food, and when abundant food reserves are formed in one season,
active height growth follows in the next. In 1934 the writer (28)
suggested that, ml1l'ked stimuln.tion of height growth resulting frolll
retention of foling!.' through the s(:cond growing senson of the nepctlcs
could not be expeetNiuulii the spring of the third senson after 11 single
fire und that a minimum of 10 ncre's wns llec!.'ssaJ'v for effective discllse
control. It is 110W l'calized that nil arca of 1,000 ncres may not be
large enough fOl' this pUl'pose if SUI'I'ollUded by all extensive source of
ftvailable inoculum.
(I)
Bln\IN,
W. L.
LlTEUA TURE CITED
1027. CO~!l'AnA'I'IVg
WI,'ItO~INI'A.
MOIU'1I0LOGY
~lycolo~ill
01"
DO'I'I!Ul!::.\CIWtTS
AND
KINDUED
H): 1-20, illWl.
(2) CIIAp.UAN,H. U.
1924. 1"OHm;T' ~mNSllllA'I'ION. k:c1. 2, 5J7pp., illus. XCII' York und London.
(3)
192(j. I'ACTOItS J)1':'I'11Il~lININ(l 1'.',1'1'1'1[.\1. HEPUOIH;C'I'ION ()J.' LONGI.I':AF
pIXI': ON (W'I'-O\'l·)Jt I.ANUS IX I.A SAI.I.E [,AHISII, I.OI'ISIANA.
Yule
l'1I1\'., 8chool Forei'ltr)" Hul. Hi, ,[·1 pp., iUus.
1932. IS 'PilE I.ONnl.gAF '1'\'1'1:: A ('I.l.IlAX? Ecolo~y l~: 328-33'1.
(5) CLI~.\lEN'I'S, F. ,1': •• and :-llJgAR, C. L. 103 L. '1'111'; m':XI,HA 01' 1"li.ro."GL Ed. 2, ·11)6 pp., illus. Kcw York. «(j) DBAICNI::SS, ,I. 1926. NI';\\' ANIl NO'I'I::WOIt'I'II1' I,'!:XGI-IV. ~'(yc()lol!;i:l 18: 236-255. (7) 1928. NgW .AXIJ N01''''\'OH'I'IIY 1'\·X01-\'. Mycologia 20: 235-246. (S} DE~I.\ION, E. L. 1935. 'l'IlE Sll.\'ICl::I:l'l~Il.U. ASt'I':("I'S 01' '1'111> 1'()ngS'r-~'IIlB !'llOIlI,g.l! IN '1'1lE
LON 0 Io).;AI,' I'INI:: lUWW;>;.
,lollr. Forestry 33: 323-331..
(9) DICKINSON, 8.
19;33. 'i'm:: ')'ECIINIQI'N 01' 1801,,\"I'ION I;>; .\IIGlIOIlIOI,OGL Phyf.opaLhology
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