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a -Ocr /^-'
Ft. Pierce ARC Research Report RL 1978-5 Oc 9
5 .A.s. ,
REDUCTION OF FUSARIUM CROWN ROT OF TOMATO BY DRENCHING WITH CAPTAFOL'trida
R. M. Sonoda 1/
Pre-, at-, and post-transplant drenching with suspensions of captafol
(75 mg active ingredient/plant) significantly reduced the incidence of
Fusarium crown rot of Floradel tomato in a field experiment. The treatments
delayed fruit production but did not appear to reduce yield or quality.
Captafol as a post-fumigation, pre-plant over-the-bed spray (6 Ib per acre)
did not significantly reduce the.number of plants affected by crown rot.
No effect on fruit maturity was noted with this treatment, suggesting that
higher dosages should be tested as over-the-bed sprays.
Crown rot of tomatoes incited by Fusarium oxysporum causes heavy losses
on some farms in southeast Florida (2). Attempts to control the disease by
applying fumigants sealed with plastic mulch have been unsuccessful (5).
Although a source of resistance to this diseasehas been found (4), no resist-
ant commercial variety is yet available.
In Ohio, captafol was found to delay onset of Fusarium crown rot and
permitted harvesting of near-normal yields (1). Captafol has received a
24(c) label in Ohio for use in greenhouse tomato culture. As registered, 24
Ibs of the fungicide in 14,000 gallons of water, are watered-in after steam-
The tests below were conducted to develop methods of using captafol
under field conditions in Florida.
Materials and Methods
Beds in a commercial farm in Jupiter, Florida, which had had tomatoes
affected by Fusarium crown rot the preceding year were fumigated with methyl-
bromide (98%) and chloropicrin (2%). Floradel tomato seedlings were grown
in shredded sphagnum peat moss: horticultural vermiculite in 'Speedling'
trays by the grower prior to transplanting.
Captafol (Difolatan 4F) (75 mg/hill as 100 ml of 750 ppm active ingred-
ient suspension) was applied as a drench in the manner described below.
Planting holes were made in polyethylene mulch about one month after fumiga-
tion and the following treatments made: 1) 100 ml of suspension poured in
planting hole, transplants placed in hole and soil around hole moved over
and against roots and attached planting mix. 2) transplants placed in hole
and 100 ml of captafol solution poured on root and planting mix attached to
roots, roots and mix covered immediately with soil; 3) planting hole
drenched with captafol, transplant put in hole, roots and attached mix
drenched with 1000 ppm active ingredient benomyl suspension, roots and mix
covered immediately with soil; 4) plants and attached mix covered with
1/ Associate Professor; University of Florida, Institute of Food and
Agricultural Sciences, Agricultural Research Center, Fort Pierce.
soil and 100 ml captafol poured on soil at base of plant; 5) no.fungicide
applied. There were five replicates of 17 plants each per treatment in a
randomized complete block. Periodic observation of plant growth and poss-
ible symptoms of phytotoxicity were made. Estimates of fruit load were
made immediately preceding first harvest and several times thereafter.
Fruit load estimates were made by counting fruits 4 oz or heavier and esti-
mating their weights at 1 oz intervals. At the end of the harvest period,
incidence of vascular discoloration at the base of the stem and in the
roots was recorded by cutting plants at the soil line and exposing the
vascular tissue. The number of dead plants were counted at the same time.
In a second test, four days after the beds were fumigated, the plastic
mulch used to cover the beds was removed and 750 ppm active ingredient sus-
pension of captafol sprayed on the b'ed surface with a hand-held boom type
sprayer at a pressure of 20 lb/ in2 and a rate of 6 Ib/acre. After spray-
ing, the beds were re-covered with the plastic mulch. There were four
replicates of 18 ft each of treated and untreated beds. The experiment
was repeated in another area of the same field. Floradel seedlings were
transplanted one ft apart to the beds one month after treatment. Three
months after treatment disease incidence was rated by cutting stems at the
soil line and exposing the vascular tissue. The number of dead plants were
also counted at the same time.
Results and Discussion
Captafol as pre-, at- and post-transplanting drenches significantly
reduced the incidence of plants with Fusarium crown rot (Table 1). There
were, however, phytotoxicity symptoms consisting of slower plant growth,
and delayed fruit set and concomittant delay in maturation of fruit. The
order of growth rate for the treatments from fastest to slowest was 5, 4,
1, 2, 3. Fruit load estimates (Table 2) indicated that yield may not have
been reduced and actually may have been enhanced. Further testsare needed
to confirm this as the interval between the earlier fruit load estimates
should have been closer. Although yields generally drop near the end of
the harvest, the drop in yield at the end of the picking period in the
control treatment is partially due to Fusarium crown rot. Moreplants were
affected by the disease in this treatment than in the other treatments.
Fusarium crown rot greatly affects yields near the end of harvest (4).
The plots were harvested by the grower beginning on April 5.' Although
plants were still full of fruit, harvest was terminated on May 9 due to
economic reasons. In previous tests, captafol as Difolatan 80Wused at
1/2 lb per gallon of water as a root dip treatment to protect tomato trans-
plants against Pythium and Rhizoctonia damp-off caused a slight delay in
plant growth with no reduction in yield (3). The incidence ofFusarium
crown rot in the experiment area was relatively low. Other areas of the
same planting had as much as 100% infection with 20% of plants killed.
In one Difolatan-over-the-bed spray test, 38% of plants in the un-
treated beds were affected by Fusarium crown rot and 32% in treated beds.
In the second test, 52% of the plants in untreated beds were affected by
Fusarium crown rot and only 28% in treated beds. The differences were
not statistically significant. Further tests with higher dosages of
captafol as over-the-bed sprays are warranted since no phytotoxicity
symptoms were noticed. In Ohio where four times as much captafol was
used on a per acre basis phytotoxicity has not been reported (1).
Further tests with captafol are warranted as these results indicate
that significant reduction in incidence of Fusarium crown rot can be
achieved with the use of this chemical.
Table 1. Effect of captafol and captafol plus benomyl drenches on
Fusarium crown rot of tomato in a commercial field in
Jupiter, Florida 1.
% plants with % plants with
basal vascular foliar
Treatment lesions symptoms
1. captafol applied to roots
and attached planting mix 3.5 a 0 a
2. captafol applied to planting
hole prior to planting 17.6 a 1.2 a
3. captafol applied to base
of plant after planting 7.0 a 1.2 a
4. captafol applied to planting
hole and benomyl applied to
roots and planting mix 3.5 a 1.2 a
5. no drench 49.5 b 16.5 b
1/ Amount and concentration of fungicides:
One hundred ml of a 750 ppm active ingredient suspension of captafol
One hundred ml of a 1000 ppm active ingredient suspension of benomyl
2/ Means followed by the same letter are not significantly different
at the 5% level DNMRT.
Table 2. Estimated weight of fruit heavier than four oz in oz
on plants treated with captafol 1A
Time of estimate
1. captafol applied to
root & attached planting
2. captafol applied to
planting hole prior
3. captafol applied to
base of plant after
captafol applied to
planting hole and
benomyl to roots and
attached planting mix
5. No drench
April 21 May 6 May 15
30.9 a 44.5 ab 34.0 a
29.9 a 47.7 ab 26.7 ab
24.3 a 37.9 b 22.8 b
33.5 a 50.4 a 34.0 a
25.7 a 22.7 c 12.1 c
1/ Plants transplanted and drenched with fungicides on December 9, 1977.
First grower harvest on April 5, last on May 9.
2/ Amount and concentration of fungicides: One hundred ml of a 750 ppm
active ingredient suspension of captafol, one hundred ml of a 1000 ppm
active ingredient suspension of benomyl.
3/ Means followed by the same letter are not significantly different at
the 5% level DNMRT.
1. Rowe, R. C. and J. D. Farley. 1978. Control of Fusarium crown and
root rot of greenhouse tomatoes by inhibiting recolonization
of stem-disinfested soil with captafol drench. Phytopath-
2. Sonoda, R. M. 1976. The occurrence of Fusarium root rot of tomatoes
in south Florida. Plant Dis. Reptr. 60:271-274.
3. Sonoda, R. M. 1974. Control of tomato transplant damp-off.
Plant Dis. Reptr. 56:840-842.
4. Sonoda, R. M., J. Marois, and J. J. Augustine. 1978. Fusarium
crown rot of tomato in Florida. Fla. State Hort. Soc. 91:
5. Sonoda, R. M. and R. T. McMillan, Jr. 1976. Comparison of wide
spectrum biocides in the field on Fusarium crown rot of
tomato. Ft. Pierce ARC Research Report RL 1976-1.