131
VOL. 53, NO. 3, CAN. PLANT DIS. SURV. SEPT. 1973
OCCURRENCE AND POPULATION DENSITIES OF NEMATODES
ASSOCIATED WITH FORAGE CROPS IN EASTERN CANADA
J.L. Townshend,' C.B. Willis: J. W. Potter,'and J . Santerr;
Abstract
Nine genera of p l a n t p a r a s i t i c nematodes w e r e a s s o c i a t e d With f o r a g e
c r o p s i n 560 f i e l d s sampled i n e a s t e r n Canada d u r i n g 1967- 72. Root- lesion,
pin,
s p i r a l , and root- knot nematodes w e r e p r e s e n t i n 961, 741, 711, and
51%, r e s p e c t i v e l y , of a l l f i e l d s sampled: s t u n t , r i n g ,
c y s t , dagger, and
Rootneedle nematodes w e r e found i n s m a l l e r p r o p o r t i o n s of t h e f i e l d s .
l e s i o n nematodes had t h e g r e a t e s t p o p u l a t i o n
densities
in
soils.
P o p u l a t i o n d e n s i t i e s of r o o t - l e s i o n and root- knot nematodes were g r e a t e r i n
r e d c l o v e r ( T r i f o l i u m r a t e n s e ) r o o t s t h a n i n a l f a l f a (Medica 0 SatiVa)
roots e x c e p t i n New B
r
b D e n s i t i e s of r o o t - l e s i o n nematodzs i n r o o t s
of b i r d s f o o t t r e f o i l (Lotus c o r n i c u l a t u s ) w e r e h i g h e s t i n P r i n c e Edward
Island.
Root-knot n z d e s w e r e n o t recovered from r o o t s of f o r a g e
g r a s s e s from O n t a r i o and Quebec. Cyst nematodes were recovered o n l y from
r o o t s of r e d clover and white c l o v e r (Trifolium r e p e n s ) .
RBsum6
Durant l a p e r i o d e de 1967-72, n o t r e enquete a r e v e l 6 l a presence de
neuf genres de nematodes p a r a s i t e s des p l a n t e s a s s o c i e s a d e s c u l t u r e s de
plantes fourrageres,
dans 560 champs e c h a n t i l l o n n e s dans l e s provinces de
l e e s t du Canada.
D e s Pratylenchus,
Paratylenchus, Helicotylenchus,
et
Meloidoqvne e t a i e n t p r e s e n t s dans 96, 74. 71. e t 51 pour- cent de t o u s l e S
champs Bchantillonnes;
des Tylenchorhynchus Criconemoides, Heterodera,
Xiphinema, e t Lonqidorus, dans une p l u s p e t i t e p r o p o r t i o n d e s champs. Les
p o p u l a t i o n s de P r a t v l e n c h u s B t a i e n t l e s p l u s denses dans t o u s l e s s o l s .
L e s p o p u l a t i o n s de P r a t y l e n c h u s e t de Meloidoqvne B t a i e n t p a r t o u t p l u s
denses dans l e s r a c i n e s de T r i f o l i u m p r a t e n s e que dans celles de Medicaqo
sativa,
sauf
au Nouveau-Brunswick.
La d e n s i t e des p o p u l a t i o n s de
P r a t y l e n c h u s dans l e s r a c i n e s d e Lotus c o r n i c u l a t u s B t a i t p l u s grande a
1 ' I l e du Prince-Edouard.
L e s Meloidosvne B t a i e n t a b s e n t s d e s r a c i n e s de
graminties f o u r r a g 6 r e s a u Quebec e t en Ontario, t a n d i s que l e s Heterodera
n ' e t a i e n t p r e s e n t s que dans l e s r a c i n e s d e
pratense e t
repens.
z.
Introduction
I
The p o t e n t i a l t h r e a t o f p l a n t p a r a s i t i c
nematodes to f o r a g e production i n e a s t e r n
Canada w a s recognized by W i l l i s and Thompson
(16, 17) when t h e y r e p o r t e d t h e presence and
nematodes,
abundance
of
root- lesion
P r a t y l e n c h u s spp.,
and e i g h t o t h e r g e n e r a
associated
with
forage
legumes i n t h e
Maritime Provinces.
E a r l i e r , numerous p i n
nematodes, Paratylenchus spp., w e r e recovered
from t h e root zone of r e d c l o v e r i n Quebec
a l o n g w i t h s p e c i e s o f f i v e o t h e r genera ( 3 ) .
Nematoloqists ,
Research
Station.
A g r i c u l t u r e Canada, Vineland S t a t i o n , O n t a r i o
LOR 2EO.
P l a n t P a t h o l o g i s t , Research
Station,
A g r i c u l t u r e Canada, Charlottetown, P.E.I.
Nematologist,
Research
Station,
A g r i c u l t u r e Canada, Ste-Foy, Quebec.
r.
Subsequently, W i l l i s and
his
associates
r e p o r t e d , i n 1971, t h e p r e s e n c e and abundance
of e i g h t p l a n t p a r a s i t i c nematode g e n e r a
a s s o c i a t e d w i t h t h r e e f o r a g e legumes i n Nova
S c o t i a ( 1 8 ) . P o t t e r and Townshend (10) have
observed t h e p r e s e n c e of e i g h t genera of
nematodes i n s o i l samples from f o r a g e c r o p
fields
throughout O n t a r i o .
During t h e s e
y e a r s and e a r l i e r , t h e nematology group i n
t h e Entomology Research I n s t i t u t e , Ottawa,
have noted i n t h e annual r e p o r t of t h e
Canadian P l a n t Disease Survey and i n t h e
Canadian
Insect
Pest
Review
isolated
incidences
of
nematodes a s s o c i a t e d w i t h
f o r a g e legumes and
grasses
in
Canada.
Coordinated surveys of f o r a g e c r o p s w e r e
conducted i n 1967 and 1968 i n southwestern
O n t a r i o and i n 1971 and 1972 i n e a s t e r n
Ontario,
Quebec,
Prince
Edward
Island
(P.E.I.),
and New Brunswick (N.B.).
Though
t h e s e were c a r r i e d o u t o v e r s e v e r a l y e a r s ,
t h e d a t a are compiled i n a s i n g l e paper t o
p r o v i d e a broad i n p r e s s i o n of t h e occurrence,
d i s t r i b u t i o n , and numbers of p l a n t p a r a s i t i c
nematodes a s s o c i a t e d w i t h f o r a g e c r o p s i n
eastern Ontario.
132
VOL. 53, NO. 3, CAN. PLANT D1S. SURV. SEPT. 1973
Materials and methods
A l l c o u n t i e s of southwestern O n t a r i o w e r e
sampled i n 1967 and 1968.
Sampling r o u t e s
r a d i a t e d from t h e w e s t e r n t i p of Lake O n t a r i o
through t h e s e c o u n t i e s , and samples were
t a k e n a t 5-mile i n t e r v a l s where p o s s i b l e .
Forage f i e l d s i n e a s t e r n O n t a r i o w e r e sampled
i n 1971. A t approximately 10-mile i n t e r v a l s
samples were taken along two p a r a l l e l routes
through t h e c o u n t i e s along t h e n o r t h e r n shore
o f Lake O n t a r i o and t h e S t . Lawrence River,
and i n t h e Ottawa Valley.
I n t h e province of
Quebec, f o r a g e f i e l d s s e l e c t e d a t random w e r e
sampled i n 1971 and 1972 i n c o u n t i e s s o u t h
and east o f Montreal and i n c o u n t i e s along
t h e n o r t h s h o r e of t h e S t . Lawrence River
w e s t and e a s t of Quebec C i t y . Forage f i e l d s
i n P.E.I.
w e r e sampled i n t h e p r o v i n c e ' s
t h r e e c o u n t i e s i n 1971.
Forage
fields
sampled i n N.B. i n 1972 w e r e also s e l e c t e d a t
random i n c o u n t i e s w i t h s i g n i f i c a n t f o r a g e
production.
Samples w e r e t a k e n d u r i n g September and
October i n P.E.I.
and N. B., d u r i n g J u l y and
August i n Quebec, and d u r i n g May-August i n
Ontario.
I n Quebec, N.B.,
and P.E.I.,
soil
c o r e s were t a k e n t o a depth of 20-25 c m
through t h e r o o t zone of randomly s e l e c t e d
p l a n t s of t h e predominant f o r a g e legume,
whereas i n O n t a r i o cores w e r e taken through
the root
zone of a l l t h e legume and g r a s s
s p e c i e s p r e s e n t . The s o i l cores from each
f i e l d w e r e bulked t o provide a 1-2 kg sample.
Root samples were c o l l e c t e d from a l l f i e l d s
e x c e p t t h o s e sampled i n southwestern O n t a r i o
d u r i n g 1967 and 1968. Ten r o o t systems of
each legume and g r a s s s p e c i e s w e r e t a k e n from
Ontario f i e l d s .
I n t h e o t h e r p r o v i n c e s , up
to 25 root systems o f o n l y t h e predominant
legume were taken.
i n a greenhouse a t 22 C. A f t e r 8 weeks t h e
s o i l was allowed to d r y ; r o o t s were t h e n
snaken f r e e of s o i l , and 5g of r o o t w e r e
p l a c e d i n a Baermann pan f o r 2 weeks.
Root samples of legumes and g r a s s e s were
washed free of s o i l and t h e f e e d e r roots w e r e
trimmed
from t h e main r o o t s .
Migratory
nematodes i n t h e O n t a r i o and Quebec samples
were e x t r a c t e d from 5g of f e e d e r roots i n
Baermann pans f o r 2 weeks, and from l o g of
f e e d e r r o o t s i n a m i s t i f i e r f o r 1 week f o r
t h e samples from N.B. and P.E.I.
All
nematode
counts
and
generic
identifications were
done
by
using
a
dissecting
microscope.
The
population
d e n s i t y of each genus of p l a n t p a r a s i t i c
nematode was recorded as t h e number p e r 0.45
kg of s o i l and as t h e number p e r g of d r y
r o o t . A f t e r counting, a l l nematode specimens
were
killed
and
fixed
for
species
identification.
A l l s o i l and root samples c o l l e c t e d i n
O n t a r i o and Quebec were processed a t Vineland
Station,
Ontario,
while t h o s e from t h e
Maritime
provinces
were
processed
at
Charlottetown, P.E.I.
Results
Soils
from
O n t a r i o and Quebec w e r e
g e n e r a l l y heavy loams o r c l a y s , w h i l e t h o s e
from New Brunswick and P r i n c e Edward I s l a n d
w e r e g e n e r a l l y sandy loams.
Frequency of occurrence
Nine p l a n t p a r a s i t i c nematode genera w e r e
associated with forage crops i n
eastern
1).
Root
lession
Canada
(Table
(Pratylenchus) pin (Paratylenchus)
spiral
I n 1971-72 p l a n t s t a n d s w e r e determined
i n a11 f i e l d s :
i n southwestern O n t a r i o i n (-us),
and
root- knot
nematodes o c c u r r e d i n more t h a n
1967-68, t h e p e r c e n t a g e of expected p l a n t
%
%
i%
?
sampled. The frequency of
s t a n d w a s determined as
based
on
t h esdlei%
knowledge of t h e l o c a l i n d u s t r y and p a s t o c c u r r e n c e of t h e r o o t - l e s i o n nematode va&.ed
from province t o p r o v i n c e by 7% and of t h e
performance.
root- knot nematode by 45%.
The Baermann pan t e c h n i q u e (14) w a s t h e
Root-knot
nematode w a s d e t e c t e d more
b a s i c method f o r t h e e x t r a c t i o n of m i g r a t o r y
nematodes from a l l s o i l samples c o l l e c t e d i n f r e q u e n t l y i n s o i l s of Quebec and e a s t e r n
when
t h e b i o a s s a y w a s used I n
e a s t e r n Canada. Each s o i l sample was mixed O n t a r i o
the
Baermann
pan
method.
and passed through a 2 nun s c r e e n t o remove a d d i t i o n t o
large roots.
Migratory
nematodes
were E x t r a c t i o n w i t h t h e Baermann pan i n d i c a t e d
t h a t o n l y 22% and 37% of t h e s o i l s from
e x t r a c t e d from 50-g subsamples f o r 1 week.
Quebec and e a s t e r n O n t a r i o , r e s p e c t i v e l y ,
The
I n e a s t e r n O n t a r i o and Quebec, c y s t and were i n f e s t e d w i t h root- knot nematode.
root- knot nematodes w e r e a l s o d e t e c t e d i n t h e b i o a s s a y d e t e c t e d root- knot nematodes i n an
a d d i t i o n a l 14% and 34% of
the
fields,
samples of heavy s o i l s w i t h a Fenwick can ( 4 )
Examination of f o r a g e legume
and a b i o a s s a y , r e s p e c t i v e l y .
These methods r e s p e c t i v e l y .
by Baermann roots from e a s t e r n O n t a r i o i n d i c a t e d a n o t h e r
supplemented
data
obtained
8% of f i e l d s i n f e s t e d .
I n southwestern
e x t r a c t i o n on t h e frequency of occurrence of
b o t h nematodes and provided c y s t s f o r s p e c i e s O n t a r i o , w i t h o u t a b i o a s s a y o n l y 36% of
i d e n t i f i c a t i o n . With t h e Fenwick can c y s t s sampled f i e l d s w e r e found to be i n f e s t e d i n
were
recovered
from
50-g
a i r - d r i e d 1967-68.
subsamples.
For t h e b i o a s s a y , a
celery
I n P.E.I.,
t h r e e o t h e r nematode genera
s e e d l i n g w a s grown i n t h e remainder of t h e
o r i g i n a l s o i l sample i n a 8-an c l a y pot h e l d also occurred i n more t h a n 50% of t h e f i e l d s
,
,
,
133
V O L . 53, NO. 3, CAN. P L A N T DIS. SURV. SEPT. 1973
Table 1.
Percentage of forage crop f i e l d s i n f e s t e d with p l a n t p a r a s i t i c nematodes i n e a s t e r n Canada
~
Percentage of f i e l d s infested'
~
Nematode
S.W. Ontario
E . Ontario
1967-68
1971
Quebec
1971-72
i n indicated a r e a s and year
~
New Brunswick
1972
Prince Edward Island
1971
Eastern Canada
1967-72
Root-lesion
94
100
93
100
100
96
Pin
85
90
63
61
87
74
Spiral
75
80
66
59
65
71
Root-knot
36
79
36
57
81
51
stunt
43
51
6
24
73
30
cyst
38
37
20
22
71
34
Ring
10
10
11
69
73
26
Dagger
15
3
4
4
5
6
Needle
0
0
0
0
3
0.5
99
71
248
51
91
F i e l d s sampled
560
% I n f e s t a t i o n a s determined from s o i l and from r o o t s of forage legumes (Prince Edward I s l a n d , New
Brunswick) o r forage legumes and grasses (Ontario, Quebec). A c e l e r y bioassay was a l s o used t o d e t e c t rootknot nematodes i n e a s t e r n Ontario and Quebec.
Table 2.
Population density of p l a n t p a r a s i t i c nematodes i n i n f e s t e d samples of s o i l from forage crop f i e l d s i n
e a s t e r n Canada
Mean and range i n number of nematodes per 0.45 kg ( l b ) of s o i l
Province
Pin
Spiral
Southwestern
Ontario
810
20- 6,500
770
40- 4,200
830
20-7,660
Eastern Ontario
1,620
50-11,700
2,040
50-13,600
820
50- 8,300
New Brunswick
Prince Edward
Island
Quebec
I
Root-lesion
Root-knot
Stunt
cyst
1
Ring
Dagger
Total
2
390
20-4,900
280
20-3,600
450
10- 7,300
170
10- 650
130
20-500
2,420
560
100-2,100
340
50-1,250
530
50- 1,700
80
10- 150
40
20- 50
4,810
50-6,300
470
20- 3,900
550
50-5,400
940
20-5,200
110
50- 300
190
20- 1,200
90
250
70
10-100
1,490
50-
2,100
200- 7,160
2,360
110-18,050
510
40-1,990
1,500
50-7,850
420
50-1,330
910
40- 3,750
320
40-2,130
330
40-630
4,880
2,800
310-18t370
1,370
100-11,860
250
50-1,350
1,090
100-8,750
300
50-2,100
1,440
100-10,000
150
50- 770
30
10- 50
5,930
670
890
300
760
180
100
1,290
1
All2
1,450
1,100
3,1302
1
Cyst l a r v a e .
'
The means i n t h e "Total" column and t h e " A l l " row, and t h e grand mean were determined from t h e o r i g i n a l
d a t a and n o t from averaging t h e means i n t h e t a b l e .
V O L . 53, NO. 3, CAN. P L A N T DIS. SURV. SEPT. 1973
134
sampled: s t u n t (Tylenchorhynchus) and r i n g
(Criconemoides) nematodes o c c u r r e d i n 73% of
t h e f i e l d s , and c y s t l a r v a e (Heterodera) i n
71%.
The
needle
(Lon i d o r u s
nematode
occurred i n 6 9 % of t h e &;led
i n N.B.
-
Soil
samples
I n e a s t e r n Canada,
a l t h o u g h t h e v a r i o u s p r o v i n c e s w e r e sampled
i n d i f f e r e n t y e a r s and a t d i f f e r e n t times i n
a season, r o o t - l e s i o n nematodes w e r e p r e s e n t
in
t h e g r e a t e s t numbers (1,450/0.45
kg)
followed by p i n (1,100/0.45
k g ) , root- knot
(890/0.45 k g ) , c y s t (760/0.45 k q ) , and s p i r a l
nematodes (670/0.45 kg) (Table 2).
I n each
p r o v i n c e , one of t h e f o u r nematode genera
o c c u r r i n g most f r e q u e n t l y i n e a s t e r n Canada
(Table 1 ) was always dominant i n terms of
s o i l p o p u l a t i o n d e n s i t y , although n o t always
t h e same nematode was dominant i n every
province. The mean of t h e t o t a l numbers of
a l l nematode genera p e r 0.45 kg of s o i l f o r
each province ( T o t a l
column,
Table
2)
probably r e f l e c t s t h e d i f f e r e n c e s i n sampling
times, season, and year. The p o s i t i o n of t h e
mean r e l a t i v e t o t h e extremes of t h e ranqe
2)
a
indicates a
Poisson
-
Root samples
R o o t l e t s of f o r a g e legumes
w i t h r o o t - l e s i o n , root- knot,
and c y s t nematodes (Table 3 ) . O f t h e legumes
sampled i n e a s t e r n Canada, r e d c l o v e r w a s t h e
where
most s e v e r e l y i n f e s t e d e x c e p t i n N.B.,
a l f a l f a was more h e a v i l y i n f e s t e d .
Rootl e s i o n nematodes were most numerous i n r e d
c l o v e r r o o t s i n each province r e g a r d l e s s of
sampling t i m e and method of e x t r a c t i o n . Red
c l o v e r r o o t s also c o n t a i n e d t h e most r o o t knot nematodes i n each province e x c e p t N.B.
Cyst nematodes w e r e found o n l y i n roots of
red clover i n a l l provinces except i n eastern
O n t a r i o , where t h e s e nematodes were recovered
a l s o from w h i t e c l o v e r roots; none w e r e found
i n e i t h e r a l f a l f a or b i r d s f o o t t r e f o i l .
Only
r o o t - l e s i o n nematodes were recovered from
g r a s s e s sampled i n e a s t e r n
Ontario
and
Quebec.
were i n f e s t e d
Population d e n s i t y
Table 3.
f o r each nematode (Table
skewness
approximating
distribution.
The mean p o p u l a t i o n d e n s i t y r e l a t i v e t o
the extremes of t h e range aqain approximated
t h e Poisson d i s t r i b u t i o n .
P o p u l a t i o n d e n s i t y o f p l a n t p a r a s i t i c nematodes i n i n f e s t e d r o o t s of f o r a g e legumes and g r a s s e s i n e a s t e r n Canada
Mean and range i n number of nematodes p e r g d r y r o o t l e t s
Location
Eastern Ontario
Quebec
New Brunswick
P r i n c e Edward I s l a n d
All2
Crop and number
of samples
Root- lesion
Root-knot
A l f a l f a -61
Red c l o v e r - 31
Birdsfoot t r e f o i l -4
White c l o v e r - 1 3
Bromegrass - 3 3
Timothy - 3 3
Orchard g r a s s - 12
Reed c a n a r y g r a s s - 2
1,070
A l f a l f a - 122
Red c l o v e r - 95
Birdsfoot t r e f o i l - 3
Bromegrass -10
Timothy -10
Orchardgrass - 4
660
1,250
230
530
630
50
20- 6,670
100- 1 , 2 0 0
300- 1,000
50
A l f a l f a - 24
Red c l o v e r - 2 2
B i r d s f o o t t r e f o i l -5
1,640
1,700
460
90-13,300
60- 6,700
70950
5,900
1,540
1,840
A l f a l f a - 22
Red c l o v e r -61
Birdsfoot t r e f o i l -8
1,840
7,450
7,400
10- 15,400
170- 46,700
60- 33,000
300
7,300
A l f a l f a - 229
Red c l o v e r - 2 0 9 ,
B i r d s f o o t t r e f o i l - 20
1,060
3,440
3,310
2,500
150
1,100
1,300
1,300
3,380
290
10- 13,400
10- 15,700
20370
80- 15,700
10- 7,400
30- 8,000
70- 18,500
290
2,260
9,500
30- 16,100
40- 39,200
280
0
0
0
10- 1,100
10- 1 , 9 0 0
2,090
4,640
2,560
2,050
0
0
0
0
0
0
0
760
2,410
5,930
1,320
i
cyst1
2,050
0
0
0
0
30- 12,050
10- 54,600
2,560
0
0
0
300-23,400
180- 5,400
260- 4,700
50670
80- 38,400
20- 2,700
Total'
0
0
0
0
0
0
0
0
1,570
5,380
150
1,350
1,300
1,300
3,380
290
0
260
0
0
0
0
0
10-1,000
0
0
0
0
1,340
3.550
3,150
5 30
630
50
0
3,540
2,390
1,810
0
440
0
30-
0
80-
0
80
0
770
20-
770
120
0
0
300
30- 1,200
0
0
0
270
0
0
1,950
12,900
8,010
1,760
6,540
4,370
c y s t larvae.
The means i n t h e " Total" column and t h e " A l l " row, and t h e t h r e e grand means were determined from t h e o r i g i n a l d a t a and n o t from averagi n g t h e means i n t h e t a b l e .
C o r r e l a t i o n of nematode p o p u l a t i o n s and p l a n t
stands
Total
p o p u l a t i o n s of p l a n t p a r a s i t i c
nematodes ( a l l genera) a s s o c i a t e d w i t h f o r a g e
c r o p s i n southwestern O n t a r i o i n 1968 w e r e
n e g a t i v e l y c o r r e l a t e d w i t h t h e p e r c e n t a g e of
expected
plant
stand
(r=-0.2440;
P(O.l)=0.2306).
P o p u l a t i o n s of r o o t - l e s i o n
and root- knot nematodes w e r e also n e g a t i v e l y
(re-0.4503:
c o r r e l a t e d with p l a n t
stand
P(0.1)=0.2306
and r-0.5287;
P(0.1)=0.4124,
r e s p e c t i v e l y ) . I n contrast, p o p u l a t i o n s of
t h e o t h e r genera w e r e p o s i t i v e l y c o r r e l a t e d
w i t h p l a n t s t a n d , a s w e r e some comparisons
u s i n g d a t a from 1971 sampling sites.
V O L . 53, NO. 3, CAN. PLANT D I S . S U RV . w
Discussion
The genera of p l a n t p a r a s i t i c nematodes
r e p o r t e d i n t h i s s t u d y t o be a s s o c i a t e d w i t h
forage crops a r e s i m i l a r t o those previously
r e p o r t e d from f o r a g e c r o p s i n Nova Scotia
( 1 8 ) , O n t a r i o ( l o ) , New J e r s e y ( 6 ) , Maryland
( 5 ) , North C a r o l i n a ( 7 ) , Texas (81, Kentucky
(2) ,
and
Minnesota
(12 )
Tentative
i d e n t i f i c a t i o n s o f nematode s p e c i e s i n d i c a t e
t h a t , although e s s e n t i a l l y t h e same genera
a r e involved, many s p e c i e s o c c u r r i n g i n t h e
s o u t h e r n United S t a t e s a r e d i f f e r e n t from
t h o s e p r e s e n t i n e a s t e r n Canada.
.
The f r e q u e n c i e s of occurrence and t h e
p o p u l a t i o n d e n s i t i e s o f r o o t - l e s i o n nematodes
i n t h i s s t u d y are s i m i l a r t o t h o s e r e p o r t e d
from f o r a g e legume f i e l d s i n Nova S c o t i a
(18).
High p o p u l a t i o n d e n s i t i e s and high
f r e q u e n c i e s of occurrence of
root- lesion
nematodes
together
with
the
previous
demonstration o f i n c r e a s e s i n f o r a g e y i e l d
( 1 3 ) when t h e s e nematodes are c o n t r o l l e d
i n d i c a t e t h a t t h e y are
an
economically
important f a c t o r i n forage production i n
e a s t e r n Canada.
In
N.B.,
more root- knot l a r v a e were
recovered from a l f a l f a r o o t s t h a n from e i t h e r
r e d c l o v e r o r b i r d s f o o t t r e f o i l , whereas t h e
converse was t r u e i n t h e o t h e r a r e a s .
Since
e s s e n t i a l l y t h e same v a r i e t i e s of a l f a l f a and
r e d c l o v e r are being grown throuqhout e a s t e r n
Canada, t h e r e a s o n s f o r t h e s e d i f f e r e n c e s i n
d e n s i t i e s of nematodes i n r o o t s of a l f a l f a
and r e d c l o v e r between r e q i o n s a r e unknown.
They may be c o i n c i d e n t a l or may r e s u l t from
climatic f a c t o r s o r d i f f e r e n t s p e c i e s o r
s t r a i n s of t h e nematode.
The
root- knot
nematode has been shown t o reduce y i e l d s of
a l f a l f a (11) and w h i t e c l o v e r ( 1 ) .
Because
population d e n s i t i e s i n infested a l f a l f a r o o t
samples w e r e high i n t h i s survey, it i s
likely
that
root- knot
nematodes
are
economically important i n e a s t e r n Canada.
The c y s t nematode has a l s o been shown t o
reduce y i e l d s
of
forage
legumes
(9).
Although f o r a g e y i e l d s w e r e n o t measured, t h e
p i n nematode i n c r e a s e d t o high p o p u l a t i o n s
under b i r d s f o o t t r e f o i l ( I 5)
I
The survey d a t a showed t h a t r o o t - l e s i o n ,
and t o t a l nematode
population
root- knot
d e n s i t i e s w e r e negatively correlated with t h e
p e r c e n t a g e of expected p l a n t s t a n d . However,
the
wide
scatter of p o i n t s found when
nematode p o p u l a t i o n s and p l a n t s t a n d s were
plotted
graphically
suggests
t h a t such
c o r r e l a t i o n s a r e meaningless.
For example,
correlations
between
existinq
nematode
p o p u l a t i o n s and p l a n t s t a n d are based on
p l a n t s t h a t have survived nematode a t t a c k and
may
be
tolerant.
To
be
meaningful,
,
135
c o r r e l a t i o n s should be based on nematode
populations t h a t existed a t t h e t i m e a forage
s p e c i e s f a i l e d . Thus, c o n t r o l l e d f i e l d p l o t
experiments o f f e r an a l t e r n a t e method of
determining
the
p o t e n t i a l economic l o s s
caused by i n d i v i d u a l nematode s p e c i e s on
individual
forage
species.
In
such
experiments t h e range of p o p u l a t i o n d e n s i t i e s
s e l e c t e d f o r a nematode s p e c i e s might be
determined by t h e mean p o p u l a t i o n d e n s i t y
observed i n e a s t e r n Canada.
The p r e s e n t survey r e s u l t s emphasize t h e
need f o r i n t e n s i v e r e s e a r c h on a l l a s p e c t s of
nematode damage i n f o r a g e c r o p s i n e a s t e r n
Canada.
Note: see Addendum, p . 136.
Acknowledg men t
The a u t h o r s thank C. F. Marks, Research
Station,
Vineland
Station,
Ont.,
for
c o o r d i n a t i n g t h e i n i t i a l planninq of t h e s e
surveys.
Literature cited
1.
Baxter, L. W., and P. B. Gibson.
1959.
nematodes
on
E f f e c t of
root- knot
p e r s i s t e n c e o f w h i t e c l o v e r . Agron. J.
51 :603-604.
2.
Chapman, R.
A.
1954. Meadow nematodes
a s s o c i a t e d w i t h f a i l u r e of spring-sown
a l f a l f a . Phytopathology 44: 542-545.
3.
Estey, R. H.
1958. Nematodes a s s o c i a t e d
w i t h a r o o t d i s e a s e complex of r e d
clover
on t h e i s l a n d of Montreal.
F o r t i e t h Report of t h e Quebec S o c i e t y
f o r t h e P r o t e c t i o n of P l a n t s . p. 150.
4.
Goodey, J. B.
f o r work w i t h
Tech. Bull.
4 t h ed.
72 p.
5.
J e n k i n s , W.
R.
D. P. Taylor, and R. A.
Rohde.
1956.
Nematodes
associated
w i t h c l o v e r , p a s t u r e , and f o r a g e c r o p s
i n Maryland. P l a n t D i s .
Rep. 40:184186.
6.
Lau,
N.
E.,
and J. P. Reed.
1960.
Nematodes a s s o c i a t e d w i t h r e d c l o v e r i n
i t s second growth year.
Plant D i s .
Rep. 44:402-404.
7.
McGlohon, N. E., J. N. S a s s e r , and R. T.
Sherwood.
1961.
Investigations
of
plant- parasitic
nematodes a s s o c i a t e d
w i t h f o r a g e c r o p s i n North C a r o l i n a .
North C a r o l i n a Agr. Exp. S t a . Tech.
B u l l . 148.
8.
Norton, D.
C.
1959.
R e l a t i o n s h i p of
nematodes t o small g r a i n s and n a t i v e
g r a s s e s i n North and C e n t r a l Texas.
P l a n t D i s . Rep. 43:227-235.
.
The
frequency
of
occurrence
and
p o p u l a t i o n d e n s i t i e s of p i n
and
spiral
nematodes
in
soil
samples
from
all
geographical regions suggest
that
these
nematodes may a l s o a f f e c t f o r a g e crops.
r . 1973
1962. Laboratory methods
p l a n t and s o i l nematodes.
2, Min. Agr. Fish. Food,
London, H.M.S.O.
,
VOL. 53, NO. 3 , CAN. PLANT DIS. SURV. SEPT. 1973
136
9.
Norton, D. C.
1967.
Relationship of
Heterodera trifolii to some forage
Phytopathology 57:1305-1308.
legumes.
10. Potter, J. W., and J. L. Townshend.
1973. Distribution of plant-parasitic
nematodes
in
field crop soils of
southwestern and central Ontario. Can.
Plant Dis. Surv. 53:39-48.
11. Reynolds,
H.
W.
1955.
Varietal
susceptibility of
alfalfa to
two
species
of
root-knot
nematodes.
Phytopathology 45:70-72.
IL. Taylor, D. P., R. V. Anderson, and W. A.
Haglund. 1958.
Nematodes associated
with Minnesota crops. I. Preliminary
survey of nematodes associated with
alfalfa,
flax, peas, and soybeans.
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13. Thompson, L. S., and C. B. Willis.
1970.
Effect of nematicides on root lesion
nematodes and forage legume yields.
Can. J. Plant Sci. 50:577-581.
14. Townshend, J.
L. 1963. A modification
and evaluation of the apparatus for the
Oostenbrink direct cottonwool filter
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110.
15. Townshend,
J.
L.
1972. Effect of hay
components on the numbers of nematodes.
Nematologica 18: 149-151.
and L. S. Thompson. 1967.
Root-lesion nematodes associated with
forage
legumes
in
the
Maritime
Provinces.
Can. Plant
Dis.
Surv.
16. Willis, C. B.,
47 :87-88.
17. Willis, C. B.,
and L. S. Thompson. 1969.
Effect of the root-lesion nematode on
yield of four forage legumes under
greenhouse conditions. Can. J. Plant
Sci. 49:505-509.
18. Willis,
C. B.,
A. L. Henderson, D. J.
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Nematodes associated with forage legume
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Addendum
paper was submitted for authors, that plant parasitic nematodes are
Since
this
(Ward likely
a
limiting
factor
in
forage
publication, an unpublished thesis
1960) on forage nematodes in New York State production.
has come to the authors' attention.
The
Ward,
C.N.
1960.
Occurrence,
incidence of Prat lenchus and Parat lenchus
distribution and populations of plant
in New York Sta-ost
identical to
parasitic nematodes associated with
that
in
Ontario.
Helicotylenchus,
Ph.D.
forage crops in New York State.
Meloido ne and T lenchorh nchus were found
Thesis, Cornell University.
Diss.
d n t l y tian in Ongario but they were
Abstr. 21:1702. 1961.
ranked in the same order of occurrence.
In
this thesis Ward concluded, as do the present
i