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1, Ft. Pierce ARC Research Report RL-1979-10 October 1979
_ Observations on Fusarium Crown Rot of Tomato in the Winter of 1978-79
R. M. Sonoda -;,
O ABSTRACT I FED 1 80
In the winter of 1978-79, symptoms of Fusarium crown rot were
observed in Delray Beach on determinate 'Walter' tomatoes.grown.for
the mature-green market. Observations indicated that the-grower- may-'"',1i
have avoided some loss to the disease due to the more concentrated
ripening of determinate as compared to indeterminate varieties of
tomato. Losses to Fusarium crown rot have been heavy in infested soils
planted to indeterminate varieties. The incidence of the disease
was lower near irrigation ditches. A heavy incidence of the disease
was observed for the first time in Vorlex or Fumazone treated plots.
Captafol used as an at-the-time-of-planting transplant drench reduced
the severity of Fusarium crown rot in a test on a commercial farm in
North Palm Beach.
Fusarium crown rot of tomato incited by a Fusarium oxysporum was
reported from Jupiter, FL in the winter of 1974-75 (1) and has since
reduced yields of tomatoes yearly on several farms on sandy soil along
the southeast coast of Florida from Jupiter to Delray Beach. Observa-
tions made on Fusarium crown rot of tomatoes in the winter of 1978-79
and a field test using fungicide drenches are reported here.
Incidence of Fusarium crown rot
From the winter of 1974-75 until the winter of 1978-79, losses
to Fusarium crown rot were confined to a group of farms under the same
management. These farms were located in four different areas from
Jupiter to Delray Beach. The principal tomato variety planted on these
farms was the indeterminate Floradel which was picked vine-ripe. The
company abandoned farming after the winter of 1978-79 and subleased
most of their farmland. In the winter of 1978-79, only one planting,
in the North Palm Beach area, a U-pick operation of about 5 acreas of
the determinate Walter variety was planted in soil with a previous
history of the disease. About 50% of the plants in a one acre field,
transplanted November 10, 1978, had foliar symptoms of Fusarium crown
rot in late March, 1979. No Fusarium crown rot-affected plants were
found in the other 4 acres which were planted earlier. In a 198 acre
field, where the pathogen was found in the soil, and which was not
planted to tomatoes since the winter of 1973-74, (before the disease
Associate Plant Pathologist, University of Florida, Institute of Food
and Agricultural Sciences, Agricultural Research Center, Fort Pierce.
was noticed), only two of 5000 plants surveyed had foliar symptoms of
Fusarium crown rot.
A field in Delray Beach, FL, with no previous history of problems
with Fusarium crown rot, had a heavy incidence of the disease in the
winter of 1978-79. The farm was planted to the determinate varieties,
Walter, Tempo and Duke, all resistant to Fusarium wilt incited by
Fusarium oxysporum f. sp. lycopersici race 1 and race 2, but not
resistant to Fusarium crown rot. Plants in two rows of a 0.4 acre
block planted on November 1, 1978 were rated for disease severity on
February 20, February 28 and March 12, 1979. The rating system used
was 1 = no disease; 2 = plants with leaves with some yellowing and a
few lower leaves with browned margins; 3 = plants generally yellowing
and all leaves with browned margins; 4 = plants severely affected,
few green areas left on leaves, stems still green; 5 = plants dead.
There were no apparent differences in the amount of harvestable
fruit on plants rated 1 or 2. Few fruit from plants with disease
severity ratings of 3 or greater were harvested. There was a rapid
increase in the number of plants with disease severity ratings of 3
or greater between February 20 and March 12 (Table I). The first
three harvests were made on February 15, February 21 and February
26; respectively. About 70% of the crop was harvested in the first
three harvests. The field-was harvested six more times at weekly
intervals. In general, the first three harvests of determinate
tomatoes on this farm yield between 65% and 100% of the total har-
vest. The fruit are usually harvested 3-8 times, at weekly inter-
vals. The number of harvests generally increases with decreases in
ambient temperature. The more concentrated ripening of fruit on
determinate varieties of tomatoes and harvesting of these varieties
on a mature-green basis, may result in lower yield losses to Fusarium
crown rot as compared to indeterminate tomatoes harvested vine-ripe
for 2-4 months after the first fruit are mature. This hypothesis is
based on the rapid increase of severely affected plants beginning at
the time the first fruits are nearing maturity. A direct comparison
of yield losses to Fusarium crown rot of these two types of tomato
varieties will have to be made.
On March 12, 1979 plants with Fusarium crown rot severity ratings
of 3 or more were counted in five adjacent blocks planted between
November 1 and 3, 1978. Plants with severe disease symptoms were more
numerous the farther they were from irrigation ditches (Table 2).
There were 14-21 rows per block. The outside rows were 10 ft from the
irrigation ditches which were parallel to the rows. There were 5 ft
between rows. Rows, three or more rows from the ditch had about the
same number of plants with Fusarium crown rot symptoms (Table 2).
This is the first time that the author has observed a relation bet-
ween Fusarium crown rot severity and distance from irrigation ditches.
Two 0.4 acre blocks immediately adjacent to each other were
treated with two different fumigants, Vorlex and Fumazone by the
grower. These blocks were transplanted with the variety Duke on
November 1, 1979. The incidence of plants with foliar symptoms of
Fusarium crown rot in both fields was recorded on March 21, 1979.
There were more plants with foliar symptoms in the Vorlex-treated
block (71%), than in the Fumazone-treated block (48%). This is the
first time that the disease has been recorded in Vorlex or Fumazone
treated fields in Florida. In the past all fields affected with
Fusarium crown rot had been treated with Methyl bromide and chloro-
Fungicide Drench Test
A fungicide drench test with benomyl at 1000 ppm, captafol at
500 ppm and captain at 250 ppm was conducted in a field in North Palm
Beach, FL that had a history of Fusarium crown rot. Holes were made
in plastic mulch covered beds about one month after the field had
been fumigated with Vorlex by the grower. Transplants of the variety
Walter, with planting mix attached to roots, were put into the holes.
About 100 ml of one of the fungicides captain, captafol or benomyl
were poured in each hole on top of the planting mix. The holes were
then filled with soil. There were 15 plants per replicate and four
replications of each fungicide drench treatment. The check treatment
was not drenched.
Plant height, plant appearance, time of blossom formation were
checked periodically. No difference was noticed between treatments
with regard to any of these factors. In a previous experiment capta-
fol delayed growth of Floradel tomatoes in the field when applied at
750 ppm (2). At the end of the growing season, the base of the stem
of each plant was cut and the vascular tissue checked for the presence
of necrotic tissue. In addition the severity of the foliar symptoms
of the disease was rated as described above. Captafol was the only
treatment which appeared to reduce disease incidence, although not
significantly so (Table 3). Part of the discrepancy between percent
plants with vascular necrosis and percent plants with foliar symptoms
(Table 3) may be due to a delay in infection of plants drenched with
captafol. Further work is needed to determine the reasons for
greater amount of plants with necrosis in the captain or benomyl treat-
ments as compared to the untreated plants.
1. Sonoda, R. M.
2 Sonoda, R. M.
3. Sonoda, R. M.
1976. The occurrence of a Fusarium root rot of
tomatoes in south Florida. Plant Disease Reporter
1978. Reduction of Fusarium crown rot of tomato
by drenching with captafol. Ft. Pierce ARC
Research Report RL-1978-8.
1978. Estimating yield losses to Fusarium crown
rot of tomato. Ft. Pierce ARC Research Report
Table 1. Duke tomato plants with Fusarium crown rot severity ratings
of 3 or more in a commercial field in Delray Beach, Florida
Row 2/ Feb. 20 Feb. 28 March 12
1 1.1 3.2 7.7
6 12.0 27.3 50.9
1/ Transplanted November 1, 1978, rating system; 3 = plants generally
yellowing and all leaves with browned margins to 5 = plants dead.
2/ Row 1 = 10 ft from irrigation ditch, Row 6 = 35 ft from ditch.
Each row with 220 plants.
Table 2. Incidence of Walter and Duke tomato plants in different
rows and blocks with Fusarium crown rot severity ratings
of 3 or more in a commercial field in Delray Beach, FL
on March 12, 1979.
Block row 1 row 2 row 3 row 4 row 5
I 8.7 24.9 48.7 --- --
II 20.4 63.4 53.6
III 1.9 9.0 25.7 28.7 20.0
IV 6.4 9.6 31.7 41.9 42.3
1/ Planted from November 1
generally yellowing and
to November 3, 1979. Rating 3 = plants
all leaves with browned margins to 5 =
2/ Row 1 = 10 feet from irrigation ditch, other rows separated by
Table 3. Efee~-o- -at-transplanting drench with fungicides on incidence
of basal stem necrosis and foliar symptom expression incited by
Fusarium crown rot on tomatoes in a field in North Palm Beach, FL.
Treatment, ppm active Plants with/ Plants with2/ DiseaseV/
ingredient vascular necrosis foliar symptoms severity
in base of stem ($) index
captafol 500 ppm 69 ab / 23 a 1.6
captain 250 ppm 79 bc 50 b 2.2
benomyl 1000 ppm 85 c 45 b 2.0
no drench 65 a 50 b 2.2
1/ Tomato plants transplanted to Vorlex fumigated beds on November 10,
1978. Roots of transplants and attached potting mix drenched with
fungicide prior to being covered with soil. Disease recorded March
2/ Base of stem cut open with knife to determine the presence or absence
of vascular necrosis.
3/ Rating system used 1 = no disease to 5 = plants dead.
4/ Means in the same column followed by the same letter are not signifi-
cantly different at the 0.05% level. Duncan's multiple range test.
*. .. I