2007 Extension Research Report
Disease Management
THE EFFECT TIME OF CHEMIGATION AND RATE AND METHOD OF METAM
SODIUM APPLICATION ON ROOT KNOT NEMATODE SOIL POPULATION AND
PHYTOPHTHORA CAPSICI AND RHIZOCTONIA SOLANI SURVIVAL IN RAISED
PLASTIC-MULCHED SOIL BEDS
B. L. Candole and A. S. Csinos, Department of Plant Pathology, University of Georgia, Tifton Campus,
D. Wang, Department of Soil, Water, and Climate, University of Minnesota, Twin Cities Campus
37.5 gal/A sprayed then rototilled, 3) 75 gal/A
sprayed and rototilled, 4) 37.5 gal/A drip-applied
for 8 h, 5) 37.5 gal/A drip-applied for 4 h, 6) 75
gal/A drip-applied for 8 h, 7) 75 gal/A dripapplied for 4 h, and 8) methyl bromide (67%
methyl bromide + 33% chloropicrin). The
treatments were applied three weeks prior to
transplanting of BHN 640 tomato. Each bed
measured 30 ft long and 30 in wide and preirrigated for eight hours a day prior to
chemigation. Tape used was Aqua-Traxx®
Premium drip tape. Emitters were spaced one inch
apart and had a flow rate of 1.14 l/hr at 0.069
MPa. Each bed received about 250 l of water after
each drip irrigation. The experiments were
arranged in an RCBD with five replications.
The effects of the treatments on the
mortality of P. capsici, and R. solani were
determined by preparing sets of two nylon mesh
packets with one packet containing 50 R. solanicolonized beet seeds and another packet with 50
P. capsici-colonized beet seeds . Each set of
packets were inserted before treatment application
at the three preselected sites: 10 cm below the
emitter, 20 cm laterally away from the emitter,
and 30 cm laterally away from the emitter and
retrieved 10 days after exposure to the treatments.
After packet retrieval, respective colonized beet
seeds were transferred onto plates containing
Rhizoctonia- and Phytophthora- selective media.
After 48 hrs of incubation under dark at room
temperature, pathogen mortality was determined
by counting the number of beet seeds that were
negative for pathogen growth and expressed as a
percentage of the total number of beet seeds tested
for the pathogen. To determine the yield, tomato
Introduction
Methyl bromide alternatives such as
metam sodium, the precursor of the biologically
active compound methyl isothiocyanate (MITC) is
a pre-plant fumigant that can be applied through
drip irrigation in raised plastic-mulched beds. As
with other water-based alternatives, metam
sodium are distributed in the soil largely by the
water in which it was applied with. MITC were
detected at high concentrations within the 10 cm
below the emitter and concentrations diminish
beyond these locations even with increased rate of
metam sodium application. Specifically,
concentrations and residence time of MITC
towards the bed shoulders were almost
nondetectable and short, respectively. As a
consequence, Phytophthora capsici and
Rhizoctonia solani and yellow nutsedge (Cyperus
esculentus L.) survival were higher towards the
bed shoulders.
This study was conducted to determine if
the rate of application, time of chemigation and
method of metam sodium application can improve
the efficacy of MITC against the soil populations
of root knot nematode(Meloidogyne incognita)
and the survival of P. capsici, and R. solani at
preselected sites within the treated beds.
Materials and Methods
The experiment was conducted at the
Black Shank Farm of the University of Georgia’s
Coastal Plain Experiment Station, Tifton, GA on
a Fuquay loamy sand (loamy, siliceous, thermic
Arenic Plinthic Paleudults). Vapam (42% metam
sodium EC) was applied according to the
following treatments: 1) nontreated control, 2)
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fruits were hand-harvested three times from 10
plants per plot. Marketable fruits were counted
and weighed. Data on final plant stand count were
also collected. Root gall indices were determined
six weeks after transplanting and after the final
harvest.
from the emitter when applied at 75 gal/A.
Mortality of R. solani with lateral distance from
the emitter of drip applied Vapam were ranked as
follows: 0 cm (59-100%) > 20 cm (10-34%) > 30
cm (3-28%) regardless of the rate and duration of
application. Of all the fumigant treatments,
Vapam drip-applied at 37.5 gal/A for 8 h and
methyl bromide were the least effective in
reducing R. solani survival at 0 cm. Sprayed and
rototilled Vapam were the most effective at both
rates of application in reducing R. solani at 20 cm
away from the emitter but not at 30 cm away from
the emitter where the most effective treatment was
sprayed and rototilled Vapam at 37.5 gal/A.
All treatments had no effect on plant
stand (as a percentage of the base count) (Table
4). Tomato plants from plots sprayed and
rototilled with Vapam at 75 gal/A had the highest
total fruit yield but the differences in marketable
fruit yield among the treatments were not
significant. However, there was a trend toward
highest marketable fruit yield from sprayed and
rototilled Vapam (75 gal/A) treatment.
The data indicated that any of the Vapam
treatments were equally effective in reducing
RKN soil populations and consequently root gall
severity. However, drip-applied Vapam’s efficacy
against P. capsici and R. solani diminished with
lateral distance from the point of application. The
data did indicate that sprayed and rototilled
Vapam had the better chance of reducing
pathogen survival at bed shoulders. Furthermore,
there is a potential for a higher yield with sprayed
and rototilled Vapam.
Results and Conclusion
Root knot nematode (RKN) soil
populations were not significantly different
among the three preselected sites 10 days after
fumigation regardless of the method, rate and
duration of application (Table 1). Within a
preselected site, RKN populations were also not
significantly different among the fumigated plots.
The method, rate and duration of application also
had no effect on root gall severity index of
tomatoes six weeks after transplanting (6 WAT)
(Table2). At harvest time root gall index was
lowest in plots where Vapam was sprayed and
rototilled at 75 gal/A . Root gall index was not
significantly different among drip-applied Vapam
plots regardless of the application duration.
Sprayed and rototilled Vapam at both
rates of application were effective against P.
capsici at the three preselected sites (Table 3).
Mortality of P. capsici with lateral distance from
the emitter of drip applied Vapam were ranked as
follows: 0 cm (86-100%) >20 cm (54-78%) >30
cm (1-43%) regardless of the rate and duration of
application. All fumigation treatments were
equally effective at 0 cm. Sprayed and rottotilled
Vapam at both rates of application had the
tendency to be more effective in reducing P.
capsici survival than the other treatments at 20 cm
away from the emitter. At 30 cm away from the
emitter, Vapam sprayed and rototilled at 75 gal/A
was the most effective in reducing P. capsici
survival.
Sprayed and rototilled Vapam at 37.5
gal/A was effective against R. solani at all
preselected sites but ineffective at 30 cm away
Acknowledgment
The authors wish to thank Don Hickey,
Unessee Hargett, Shad Law, Buddy Powell, Brad
Russel, Clint Powell, Channing Paulk, Crystal
Simataro and Zack Moye for technical assistance.
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Table 1. The effect of rate and method of metam sodium application on the soil populations of root knot
nematode before and after fumigation and preselected sites within the treated plastic-mulched beds.
Root knot nematodes/150 cc soila
Treatment and time of observation
0 cm
20 cm
30 cm
Nontreated control
153 a (a)
80 a (a)
240 a (ab)
Vapam (37.5 gal/A) sprayed and rototilled
185 a (a)
78 a (a)
195 a (ab)
Vapam (75 gal/A) sprayed and rototilled
228 a (a)
110 a (a)
128 a (b)
Vapam (37.5 gal/A) drip applied for 8 h
150 a (a)
80 a (a)
130 a (b)
Vapam (37.5 gal/A) drip applied for 4 h
108 a (a)
78 a (a)
35 a (b)
Vapam (75 gal/A) drip applied for 8 h
88 a (a)
98 a (a)
55 a (b)
Vapam (75 gal/A) drip applied for 4 h
113 b (a)
83 b (a)
443 a (a)
20 a (a)
3 a (a)
20 a (b)
Nontreated control
135 a (a)
92 a (a)
225 a (a)
Vapam (37.5 gal/A) sprayed and rototilled
35 a (a)
73 a (a)
25 a (b)
Vapam (75 gal/A) sprayed and rototilled
128 a (a)
80 a (a)
65 a (ab)
Vapam (37.5 gal/A) drip applied for 8 h
23 a (a)
13 a (a)
23 a (b)
Vapam (37.5 gal/A) drip applied for 4 h
35 a (a)
108 a (a)
48 a (b)
Vapam (75 gal/A) drip applied for 8 h
58 a (a)
38 a (a)
30 a (b)
Vapam (75 gal/A) drip applied for 4 h
48 a (a)
18 a (a)
23 a (b)
Initial (Before Fumigation)
Methyl bromide (67% MB + 33% chloropicrin)
10 days after fumigation
Methyl bromide (67% MB + 33% chloropicrin)
8 a (a)
15 a (a)
23 a (b)
In a row, treatment means from the three preselected sites (0 cm = 10 cm below the
emitter, 20 cm
away from the emitter, and 30 cm away from the emitter) followed by the
same letters; or
treatment means within a column within an observation time followed by
the same letters in
parentheses not significantly different by DMRT at P=0.05.
a
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Table 2. The effect of rate and method of metam sodium application on root gall index of BHN 640
tomato at 6 weeks after transplant (WAT) and at harvest.
Root gall indexa
Treatment
6 WATb
Harvest
Nontreated control
2.30 a
6.10 a
Vapam (37.5 gal/A) sprayed and rototilled
1.30 b
4.80 ab
Vapam (75 gal/A) sprayed and rototilled
0.65 b
2.45 c
Vapam (37.5 gal/A) drip applied for 8 h
0.90 b
3.52 bc
Vapam (37.5 gal/A) drip applied for 4 h
1.35 b
5.00 ab
Vapam (75 gal/A) drip applied for 8 h
1.25 b
4.55 ab
Vapam (75 gal/A) drip applied for 4 h
0.70 b
3.90 bc
Methyl bromide (67% MB + 33% chloropicrin)
0.80 b
4.60 ab
Root gall index: 0 = Complete and healthy root system, no infestation; 2 = Very few small galls can
only be detected upon close examination; 3 = Small galls as in "1" but more numerous and easy to
detect; 3 = Numerous small galls, some grown together,
function of roots seriously affected; 4 =
Numerous small galls, some big galls, majority of roots still functioning; 5 = 25% of root system
severely galled and not functioning;
6 = 50% of root system severely galled and not functioning; 7 =
75% of root system
severely galled and lost for production; 8 = No healthy roots, nourishment of
plant interrupted, plant still green; 9 = The completely galled root system is rotting, plant is
dying;
10 = Plant and roots are dead.
b
Within a time of observation, treatment means with the same letters are not significantly
different by DMRT at P=0.05.
a
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Table 3. The effect of rate and method of metam sodium application on the mortality of Phytophthora
capsici and Rhizoctonia solani after 10 days of exposure at three preselected sites within the treated
plastic-mulched beds.
Mortality (%)a
Treatment and time of observation
0 cm
20 cm
30 cm
Phytophthora capsici
Nontreated control
24 a (b)
31 a (c)
29 a (cd)
Vapam (37.5 gal/A) sprayed and rototilled
85 a (a)
91 a (a)
70 a (b)
Vapam (75 gal/A) sprayed and rototilled
83 a (a)
91 a (a)
99 a (a)
Vapam (37.5 gal/A) drip applied for 8 h
100 a (a)
78 a (ab)
1 b (d)
Vapam (37.5 gal/A) drip applied for 4 h
97 a (a)
54 b (bc)
13 c (d)
Vapam (75 gal/A) drip applied for 8 h
86 a (a)
73 a (ab)
43 b (bc)
Vapam (75 gal/A) drip applied for 4 h
100 a (a)
71 b (ab)
23 c (cd)
94 a (a)
82 a (ab)
51 b (bc)
Methyl bromide (67% MB + 33% chloropicrin)
Rhizoctonia solani
Nontreated control
18 a (c)
3 a (c)
0 a (c)
100 a (a)
89 a (a)
99 a (a)
Vapam (75 gal/A) sprayed and rototilled
92 a (a)
72 a (a)
37 b (b)
Vapam (37.5 gal/A) drip applied for 8 h
59 a (b)
10 b (bc)
3 b (c)
Vapam (37.5 gal/A) drip applied for 4 h
100 a (a)
26 b (bc)
5 b (c)
Vapam (75 gal/A) drip applied for 8 h
99 a (a)
28 b (bc)
5 b (c)
Vapam (75 gal/A) drip applied for 4 h
100 a (a)
34 b (b)
28 b (bc)
Vapam (37.5 gal/A) sprayed and rototilled
Methyl bromide (67% MB + 33% chloropicrin)
51 a (b)
1 b (c)
12 b (bc)
In a row, treatment means from the three preselected sites (0 cm = 10 cm below the
emitter, 20 cm
away from the emitter, and 30 cm away from the emitter) followed by the
same letters; or
treatment means within a column and within a pathogen followed by the
same letters in
parentheses not significantly different by DMRT at P=0.05.
a
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Table 4. The effect of rate and method of metam sodium application on plant stand and fruit yield of
BHN 640 tomato.
Treatment
Plant
Total fruit
Marketable
stand (%)
yield (t/ha)
fruits (t/ha)
Nontreated control
65 a
45.76 c
35.86 a
Vapam (37.5 gal/A) sprayed and rototilled
98 a
91.81 ab
75.85 a
Vapam (75 gal/A) sprayed and rototilled
98 a
98.62 a
76.01 a
Vapam (37.5 gal/A) drip applied for 8 h
63 a
64.46 bc
45.77 a
Vapam (37.5 gal/A) drip applied for 4 h
85 a
87.42 ab
61.81 a
Vapam (75 gal/A) drip applied for 8 h
90 a
76.28 abc
51.31 a
Vapam (75 gal/A) drip applied for 4 h
95 a
78.16 ab
53.35 a
Methyl bromide (67% MB + 33% chloropicrin)
85 a
75.03 abc
54.79 a
Within a column, treatment means with the same letters are not significantly different by DMRT at
P=0.05.
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