9. Fairchild, D. 1920. Plant Inventory. (Comments on Plant Introduc
tions 42389 and 42678, zoysiagrass; and 46415, centipedegrass). U.
S. Dept. of Agr. Agr. Res. Serv. (Formerly, Inventory, Bureau of
Plant Industry).
10. Fairchild, D. 1938. The world was my garden: travels of a plant
explorer. Charles Scribner's Sons, New York, NY.
11. Finlayson, E. H. 1941. Pensacola ... a new fine-leafed bahia. South.
Seedsman, Dec. issue, 9, 28.
12. Florida Department of Agriculture and Consumer Services. 1976.
Florida turfgrass survey 1974. Crop Livestock Rpt. Serv. Fla. Dept.
Agr. Consumer Serv. Tallahassee, FL.
13. Fosberg, F. R. 1977. Paspalum distichum again. Taxon 26:201-202.
14. Horn, G. C. 1961. Establishment and maintenance of large turf areas.
Proc. Soil Crop Sci. Soc. Fla. 21:115-119.
15. Horn, G. C, A. E. Dudeck, and R. W. Toler. 1973. 'Floratam' St.
Augustinegrass: A fast growing new variety for ornamental turf re
sistant to St. Augustine decline and chinch bugs. Fla. Agr. Expt. Sta.
Cir. S-224.
16. Hume, H. H. 1929. Gardening in the lower South. The Macmillan
Company, New York, NY.
17. Jackson, J. 1987. Florida's green acres. Central Florida Business,
March 16-22. p. 21.
18. Killinger, G. B., G. E. Ritchey, C. B. Blickensderfer, and William
Jackson. 1951. Argentine bahia grass. Univ. Fla. Agr. Expt. Sta. Cir.
S-31.
19. Morton, J. F. 1973. Salt-tolerant silt grass (Paspalum vaginatum Sw.).
Proc. Fla. State Hort. Soc. 86:482-490.
20. Nutter, G. C. and R. J Allen, Jr. 1960. Floratine St. Augustinegrass:
A new variety for ornamental turf. Fla. Agr. Expt. Sta. Cir. S-123.
21. Ousley, J. E. 1963. Why I went certified. Proc. Florida Turfgrass
Association (formerly, Proc. Univ. Fla. Turf-Grass Manage. Conf.)
11:133-135.
22. Pynchon, N. 1971. New chinch resistant sod in production. Florida
Turf 4(1):6, 10.
23. Reinert, J. A. and A. E. Dudeck. 1974. Southern chinch bug resis
tance in St. Augustinegrass. J. Econ. Entomol. 67:275-277.
24. Riordan, T. P., V. D. Meier, J. A. Long, and J. T. Gruis. 1980. Reg
istration of Seville St. Augustinegrass. Crop Sci. 20:824-825.
25. Sauer, J. D. 1972. Revision of Stenotaphrum (Gramineae:Paniceae)
with attention to its historical geography. Brittonia 24:202-222.
26. Smith, C. N. and R. H. Brewster. 1968. An economic study of the
Florida cut sod industry. Econ. Mimeo Rpt. EC 69-3, Dep. of Agr.
Econ., Agr. Expt. Sta., Univ. of Florida, Gainesville, FL.
27. St. Augustine Historical Society. 1987. And the green grass grew all
around. The Florida Gazette No. 2. St. Augustine Hist. Soc, St. Au
gustine, FL.
28. White, R. W. 1958. Weed control in lawns and ornamentals. Proc.
Soil Crop Sci. Soc. Fla. 18:216-218.
29. White, R. W. 1982. Retrospective: A history of Florida Turf-Grass
Association. Proc. Fla. Turf-grass Conf. 30:13-18.
Proc. Fla. State Hort. Soc. 100:174-176. 1987.
SOLARIZATION OF SMALL VOLUMES OF POTTING SOIL FOR
DISINFESTATION OF PLANT-PARASITIC NEMATODES
R. M. GlBLIN AND S. D. VERKADE
University of Florida, IFAS
Fort Lauderdale Research and Education Center
3205 College Avenue
Fort Lauderdale, FL 33314
Additional index words. Cultural management.
Abstract. There has been considerable research to implement
solarization as a practical cultural management tool for the
control of a variety of soil pathogens and nematode parasites
in the field and in greenhouses. However, little has been
done to make this relatively simple, safe, and efficacious
strategy available to the homeowner. South Florida receives
enough solar radiation during most of the year to justify the
practice of soil solarization of potting soil by homeowners.
The subject of soil solarization is introduced, its advan
tages and disadvantages discussed, and a simple design for
its implementation suggested.
Control of plant-parasitic nematodes in potted plants is
best facilitated by cultural management. Essentially, prop
agation material is disinfested by using uninfested aerial
parts (2), heat treatment of infested tissue (10), or chemical
treatment (2). Nematode-free planting stock is then trans
planted into disinfested or sterile potting soil in sterile con
tainers. Plants are propagated away from the ground,
either on benches or indoors. There are no postplant nematicides that are presently available which will totally
eradicate nematodes once the plant is added to the pot.
Consequently, the benefits of starting clean and keeping
Florida Agricultural Experiment Station Journal Series No. 8735.
174
clean cannot be overemphasized, especially to the home
owner who has very little for the control of nematodes.
Starting with clean stock is easy in plants that are prop
agated from seed and plants such as aroids which can be
cultured vegatatively from aerial parts such as leaves or
stems. If plant parts which have been exposed to the soil
are used for propagation (ie. corms, rhizomes, etc.) some
form of disinfestation may be required. Often the infested
area can be simply excised, however since endoparasitic
nematodes are microscopic there is always a chance that
some will be missed and these will be sufficient in number
to colonize and reduce the performance or kill the potted
plant later. Another alternative is to determine a tempera
ture threshold at which the nematodes will be killed, with
out plant damage (10). Unfortunately, this is time consum
ing and not always practical. Another strategy is to start
with material that is known to be nematode-free. Whatever
strategy is employed, the planting stock must be free of
phytoparasitic nematodes prior to planting. Otherwise, all
subsequent efforts to keep the potted plant free of nema
todes will be futile.
The next step in keeping potted plants free of nema
todes involves the preparation of nematode-free soil. This
can be accomplished by physical means with an autoclave,
steam sterilizer, or an oven. Steam sterilization or autoclaving can be commercially feasible but it is too expensive to
justify for homeowners. Oven treatment of soil is possible
for small volumes. However, this treatment is often messy
and baked soil can sometimes have an unpleasant odor.
Chemical means of soil disinfestation include the use of
Chloropicrin (Chlor-O-Pic), Methyl bromide (Brom-OGas), or Metam sodium (Vapam, Fume-V, or Busan 1020).
Chloropicrin and Methyl bromide require a commercial
Proc. Fla. State Hort. Soc. 100: 1987.
fumigators license for application and will not be dis
cussed, in this paper. Vapam is feasible and recommended
when large volumes of disinfested soil mix is needed but
can be tricky and time consuming to work with because of
its phytotoxic side effects (1,2).
Soil solarization is a technique that has been utilized for
controlling many soil-inhabiting pathogens and parasites
without deliterious effects to beneficial microbes (8). Sol
arization utilizes the "greenhouse effect" where a piece of
plastic or glass which is invisible to high energy short-wave
solar radiation, but represents a partial barrier for lower
energy long-wave radiation is used to retain and slow down
the reradiation of infrared energy from the system (3).
Thus, plastic covered soil absorbs the short-wave radiation
that penetrates the plastic, thereby allowing long-wave
radiation to be trapped for heating the soil to a tempera
ture lethal for soil-pathogens.
Miami receives an annual average of about 132,000
Langleys during its 10 month growing season. The
Langley is a unit of measurement for quantifying the
amount of usable solar radiation that contacts a surface
and denotes one gram calorie per square centimeter (One
gram calorie = the heat energy necessary to raise the tem
perature of 1 gram of water 1 degree C) (3). In south
Florida, the months of April, May, June, July, and August
have mean daily solar radiation averages above 500
Langleys (Figure 1). This level of solar radiation is rela
tively high and suggests that south Florida has potential
for solarization work during these months. The only draw
back is the precipitation pattern that develops in the sum
mer. The cloudiness that comes with this weather is detri
mental because long periods of sunlight are needed for
effective solarization efforts. Solarization attempts have
been encouraging in field applications in Manatee County,
Florida, where solarization of an EauGallie fine sand re
duced the incidence of the fungus Verticillium albo-atrum
during a fall/spring double-cropping of tomatoes and the
root-knot nematode, Meloidogyne incognita during the fall
only. Solarization improved yields in tomatoes by 26% in
the fall but no significant effect was noted in the spring
(4). The major problems with field application in Florida
involve summer rainfall patterns and high water tables
which reduce soil temperature (4). The homeowner cannot
control rainfall patterns but by working with small volumes
on concrete or asphalt can increase the exposure of the soil
to be solarized by reducing soil depth. This procedure will
also control soil moisture levels.
Maximum temperatures during field solarization with
a single layer of transparent, high density, 1.5 mil
polyethylene fumigation film reached 47° C in fine sandy
loam soil and 44° C in silty clay loam soil in Davis, Califor
nia (9). The efficiency of solarization can be increased with
the use of two layers of plastic mulch. Temperatures at 10
cm for 2-layer plastic mulched, 1-layer, and bare beds were
60°, 47.5°, and 32.2° C in La Molina, Peru (5). The soil
temperature during solarization is dependent on a variety
of variables, including soil type, moisture, amount of solar
radiation, cloud cover, and thickness of plastic.
The temperature threshold for different nematode
species varies with the species and the time of exposure.
Nematodes, most plant-pathogenic fungi and bacteria, and
soil insects are killed during steam sterilization at 60-71° C
for 30 min. (8). These temperatures are rarely achieved
Proc. Fla. State Hort. Soc. 100: 1987.
AVERAGE DAILY SOLAR RADIATION
^ 600
<N
o
550
£, 500
•
•
\
g 450
| 400
§ 350
\
■ /
\
O
w 300
JFMAMJJASOND
MONTH
Fig. 1. Monthly mean daily radiation (Langleys). This figure is based
upon all usable solar radiation data, direct and diffuse, measured on a
horizontal surface and published in the monthly Weather Review and
Climatological Data National Summary for Miami, Florida through 1962.
during solarization attempts; however, lower temperatures
for longer times can be lethal to nematodes. For example,
dry heat treatment of sweetpotato seed roots at 45° C for
30 hrs killed all of the root-knot nematodes present in
roots (10). The maximum temperature range for infectivity and reproduction for root-knot nematodes is 35-40° C
(6). The foliar nematode, Aphelenchoides frageriae, which is
ectoparasitic in the bud of strawberries could be controlled
with a hot water treatment of 48° C for 20 min or 47° C
for 30 min (7). These data and our preliminary work
suggest that homogeneous soil temperatures of 47° C for
longer than 2 hours may be enough to kill most
phytoparasitic nematodes. Preliminary work at Fort
Lauderdale Research and Education Center has shown
that a simple solarization unit can be designed that pro
duces these kinds of conditions.
A proposed design for a homeowner solarization unit
would require that moist soil or sand be placed into a large
black polyethylene plastic garbage bag (132 liter, 1.2 mil),
which is sealed in a transparent plastic bag. The double
wrapped soil would then be placed on asphalt or cement
in a fully exposed area and spread to a uniform depth of
7.62 cm. Temperature can easily be monitored with a soil
thermometer. As long as the bag receives one full day of
sunlight in April, May, June, July, or August the tempera
tures will reach and exceed 45° C for more than 2 hrs. The
bag can be left exposed in the area until the solar condi
tions are right or until thermometer readings confirm that
the soil has been treated properly. The optimum time for
collecting solar radiation changes seasonally, but the best
time of the day during May and June appeared to be 2-4
P.M. (Giblin and Verkade, Unpublished observations).
The soil is then cooled and is ready for planting clean
propagation stock. Each double-bag solarization unit can
be expected to yield about 24 liters of soil and can be
reused if undamaged.
Literature Cited
1. Dunn, R. A. 1983. Home garden nematode control with vapam. Fla.
Coop. Extension Serv. Nematology Plant Protection Pointer NPPP12.
175
2. Dunn, R. A. and R. W. Henley. 1985. Nematode control for commer
cial nursery crops. Fla. Coop. Extension Serv. Nematology Plant Pro
tection Pointer NPPP-22.
3. Janick, J., R. W. Schery, F. W. Woods, and V. W. Ruttan. 1969. Plant
science: an introduction to world crops. W. H. Freeman and Co. San
Francisco.
4. Overman, A. J. and J. P.Jones. 1986. Soil solarization, reaction, and
fumigation effects on double-cropped tomato under full-bed mulch.
Proc. Fla. State Hort. Soc. 99:315-318.
5. Raymundo, S. A. and J. Alcazar. 1986. Increasing efficiency of soil
solarization in controlling root-knot nematodes by using two layers
of plastic mulch. J. Nematol. 18:628.
6. Sasser, J. N., and C. Cameron-Carter. 1982. Root-knot nematodes
(Meloidogyne spp.): Identification, morphological and physiological
variation, host range, ecology, and control, p. 21-31. In: R. D. Riggs
(ed). Nematology in the southern region of the United States. South
ern Coop. Series Bull. 276.
7. Slack, D. A. and R. D. Riggs. 1982. The bud and leaf nematodes, p.
180-181. In: R. D. Riggs (ed). Nematology in the southern region of
the United States. Southern Coop. Series Bull. 276.
8. Stapleton, J. J., and J. E. DeVay. 1984. Thermal components of soil
solarization as related to changes in soil and root microflora and
increased plant growth response. Phytopath. 74:255-259.
9. Stapleton, J. J., B. Lear, and J. E. Devay. 1987. Effect of combining
soil solarization with certain nematicides on target and nontarget or
ganisms and plant groth. Ann. Appl. Nematol. 1:107-112.
10. Thomason, I. J., S. D. Van Gundy, and H. E. McKinney. 1960. Ther-
motherapy for root knot nematodes, Meloidogyne spp., of sweetpotato
and tarragon propagating stocks. Plant Disease Reporter 44:354-358.
Proc. Fla. State Hort. Soc. 100:176-178. 1987.
PROPAGATION TECHNIQUES FOR FIVE ENDANGERED SAND SCRUB SPECIES
Nancy J. Bissett
The Natives, 453-C Champane Road
Davenport, Florida 33837
Additional index words. Prunus geniculata, scrub plum, Warea
carteri, Carter's warea, Warea amplexifolia, clasping warea,
Dicerandra cornutissima, longspurred balm, Dicerandra immaculata, Lakela's mint.
Abstract. Several seed and cutting propagation techniques
were tested for Prunus geniculata Harper, Warea carteri
Small, Warea amplexifolia (Nutt.) Small, Dicerandra cor
nutissima Huck, and Dicerandra immaculata Lakela. All five
are listed as federally endangered and are endemic to parts
of central Florida's sandhills or sand scrub. Prunus geniculata
germinated best after a period of cold moist stratification.
Both warea's, which are annuals, germinated easily from
seed, but are susceptible to damping-off fungi and
phytotoxicity from pesticides. Cuttings of D. cornutissima
taken in July and treated with a weak hormone solution de
veloped stronger root systems than those not treated. Cuttings
treated similarly for D. immaculata showed no significant
difference when treated with hormone. Both species showed
little difference from December cuttings.
The major threat to Florida's endagered plant species
is loss of habitat caused largely by human development
and a secondary threat is collection from the wild. Though
preservation of habitat is the most critical concern, another
alleviation of the problem is to bring these plants into cul
tivation in a manner in which a wide range of the genetic
diversity of each species is retained. The Center for Plant
Conservation, a national organization with member gar
dens throughout the country (2), as well as many private
nurseries have been working on propagation techniques.
Bok Tower Gardens, a member of the Center for Plant
Conservation, has sought to bring many rare and en
dangered species from central Florida's sand pine scrub
and sandhill into cultivation. The sand pine scrub commu
nity is most frequently found on white sand that is acid
This project was supported by Bok Tower Gardens as a member of
the Center for Plant Conservation.
176
and excessively well-drained. Characteristic plants include
sand pine, several scrub oaks, rusty lyonia, saw palmetto,
scrub palmetto, prickly pear, rosemary, several subshrub
mints, and buckwheats. Many species, including 4 of the 5
described here, are endemic to central Florida's scrub (1,
3).
The sandhill typically occurs on rolling hills of deep
yellow well-drained acid sands with a dominant vegetation
of turkey oak and longleaf pine with a grassy and herbace
ous understory. In this form it is a fire-based community
with fires occuring every 2 to 5 years. Where fire is
excluded more shrubby species are found. Most sandhill
communities have been converted to citrus groves and re
sidential developments. Warea amplexifolia is among those
species endemic to the sandhill (1, 3).
All five species have been listed as endangered by the
U.S. Fish and Wildlife Service. Both Prunus geniculata and
Warea amplexifolia exist in the natural areas at Bok Tower
Gardens. All five are found only in central Florida.
Propagation of these plants to increase chances of sur
vival is encouraged, but propagation material should be
taken from previously propagated plants if at all possible.
To collect seeds and cuttings from the wild, owner permis
sion is required and both the Florida Division of Plant In
dustry and the U.S. Fish and Wildlife Service should be
consulted.
Prunus geniculata
Prunus geniculata, scrub plum, of the Rosaceae is a heav
ily branched shrub averaging 3 feet tall with strongly zig
zag twigs, deciduous leaves, white five petalled blooms in
spring and sweet, juicy reddish plums that are born in
April. It occurs in scrub and sandhill ecosystems in Lake,
Polk and Highlands Counties.
Both seed and cutting propagation were attempted.
Cuttings taken mid-June failed because of a leaf disease in
the mist bed. Some callousing and a few roots had formed
and this method should be tried again. Hormone treat
ments did not appear to help or hurt. Since P. geniculata
is not a vigorous shrub, it is suggested that cuttings be
taken from young shrubs or those that have regenerated
after fire of after having been cut back.
Proc. Fla. State Hort. Soc. 100: 1987.