| Material Information
||Comparison of several wide spectrum biocides in the field on Fusarium crown rot of tomato
||Ft. Pierce ARC research report
||2, 1 leaves : ; 28 cm.
||Sonoda, Ronald M
McMillan, Robert Thomas, 1934-
University of Florida -- Agricultural Research Center
||University of Florida, Insititute of Food and Agricultural Sciences, Agricultural Research Center
||Place of Publication:
||Fort Pierce Fla
||Tomatoes -- Diseases and pests -- Control -- Florida ( lcsh )
||bibliography ( marcgt )
non-fiction ( marcgt )
||Includes bibliographical references (leaf 3).
||Statement of Responsibility:
||R.M. Sonoda and R.T. McMillan, Jr.
| Record Information
||University of Florida
||All rights reserved by the source institution and holding location.
||oclc - 69648023
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Ft. Pierce ARC Research Report RL-1976-1
Comparison of several wide spectrum biocides in the field
on Fusarium crown rot of tomato
R. M. Sonoda and R. T. McMillan, Jr.l/
In two experiments to control Fusarium crown rot of tomato in a commercial
planting, the standard treatment of about 285 lbs/tNe ted acre of a mixture
containing 33% chloropicrin and 67% methyl bromide underpolyethylene mulch
previously found to be inadequate in control perffmted aswell as or better
than other treatments including higher rates o Ar% chloro~ rin 33% methyl
bromide mixture. Plots treated with 35 lbs.; ajgve ingredient cre sodium
azide had ten times as many dead plants as the~fandactreatmt.
/ /a O '
Fusarium crown rot of tomatoes isa/ -seaseew to ith Florida (1). It
caused heavy losses on a farm near Jupiter, Fl in the wi tr of 1974-75. Beds
in fields on this farm were treated with mixture c ntaiiing 33% chloropicrin
and 67% methyl bromide at 250 to 350 lbs. per.treate4d:acre and sealed with
polyethylene mulch. The soil between plastic cbve8ae b eds were not treated.
The treatment did not adequately prevent losses to'-hhe disease (1). None of
the commercial tomato varieties currently grown in Florida are resistant to
the fungus (1). Several methods of controlling this diseaseare currently
being studied. Herein are reported two field tests; one comparing two ratios
of chloropicrin-methyl bromide mixture and the other comparing 33% chloropicrin/
67% methyl bromide, sodium azide, and 33% chloropicrin/67% methyl bromide plus
Materials and Methods
Both tests were conducted in a commercial planting near Jupiter, Florida
where about 1% of the tomato plants had been killed by the quick wilt phase of
the disease in the preceding year (1). Transplants of the tomato variety
Floradel were used in the tests. Disease severity was determined by counting
the number of plants killed by the quick wilt phase of the disease.
Test 1 This experiment compared 33% chloropicrin-67% methyl bromide and
67% chloropicrin-33% methyl bromide as fumigants under polyethylene mulch.
The treatments were applied with a tractor-mounted, three-row, nine-chisel
fumigator on raised beds on five feet centers. A 1.5 feet wide area between
the beds was not fumigated. Beds were covered with polyethylene mulch immediately
after fumigation. There was one treatment of three rows, each about 1170 feet
long to which was applied 285 Ibs/treated acre 33% chloropicrin -67% methyl
bromide. There were two replicates of three rows each of 350, 370, and 400 lbs/
treated acre of 67% chloropicrin-33% methyl bromide. These rows varied between
1/ Associate Plant Pathologists, University of Florida, Institute of Food and
Agricultural Sciences, Agricultural Research Center, Fort Pierce and
Agricultural Research and Education Center, Homestead, respectively.
900 and 1170 feet long. Tomato transplants were set 4 weeks after fumigation.
The number of plants killed by the disease was recorded four and one half months
Test 2 This experiment was conducted to determine the effect of the wide
spectrum biocide, sodium azide (Smite 15G), on the new Fusarium disease. Smite
15G (about 35 lb. active ingredient/acre) was broadcast over a 60 feet wide area
containing 13560 square feet and incorporated into the soil with a disc harrow.
Two weeks later when beds were formed in this area two alternate sets of three
rows, 215 to 240 feet long, were treated with 33% chloropicrin-67% methyl
bromide. Treatments were not randomized. An adjacent block containing 12 rows,
190 to 215 feet long was treated with 33% chloropicrin-67% methyl bromide alone.
The number of plants killed by the disease was recorded four months after trans-
Results and Discussion
Fusarium crown rot symptoms were noticed on plants in both Test 1 and
Test 2 at the time fruits were nearing maturity. The quick wilt phase (1) of
the disease was not very prevalent (Table 1) however, most of the plants were
in some stage of slow wilt (1) at the end of the harvest period, and almost
all plants inspected were infected.
Results from Test 1 (Table 1) indicate high rates of the 67% chloropicrin-
33% methyl bromide treatment had as many quick-wilt plants as the standard 33%
chloropicrin-67% methyl bromide treatment. The standard treatment did not give
satisfactory control of the disease in the preceding year (1).
Results from Test 2 (Table 2) show ten times as many plants exhibiting
the quick wilt syndrome in the rows treated with sodium azide alone as compared
to the standard 33% chloropicrin-67% methyl bromide treatment alone. The
combination of the standard treatment with sodium azide was no better than the
standard treatment alone.
Studies are being conducted to determine if the ineffectiveness of these
treatments are the result of insufficient reduction of the fungus by the wide
spectrum biocides or reintroduction of the fungus into the treated areas.
New and promising chemicals will also be tested.
Table 1. Percent tomato plants dead with Fusarium crown rot symptoms (quick wilt)
four and one half months after planting in chloropicrin/methyl bromide
fumigated soil mulched with polyethylene.
chloropicrin/methyl bromide lbs of mixture/treated acre dead plants
33/67 285 0.8
67/33 350 4.6
67/33 370 3.2
67/33 400 1.1
Table 2. Percent tomato plants dead with Fusarium crown rot symptoms (quick wilt)
four months after planting in soil treated with wide spectrum biocides
and covered with polyethylene mulch.
Treatment Ibs/treated acre dead plants
1. 33% chloropicrin/67% methyl bromide 300 0.7
2. Smite 15G 35 9.3
3. 33% chloropicrin/67% methyl bromide 300
plus Smite 15G 35 0.6
1. Sonoda, R. M. 1976. The occurrence of a Fusarium root rot of tomatoes in
south Florida. Plant Dis. Reptr. 60: 271-274.