S-1 APR 22 19688
BIG BEND HORTICULTURAL LABORATORY
Mimeo Report March 25, 1968 I.F .AS. Univ. of Florida
EVALUATION OF SELECTED FUNGICIDES FOR THE CONTROL OF PEACH SCAB,
BROWN ROT AND RHIZOPUS ROT ON MAYGOLD PEACHES AT MONTICELLO, FLA.,
by W. J. French1,2
North Florida's new and growing peach industry can realize its great
potential if control programs can be developed to protect adapted peach varieties
from diseases and insects. In northern Florida the major field and post-harvest
diseases are brown rot and blossom blight (Monilinia fructicola (Wint.) Honey),
scab (Cladosporium carpophilum Thum.), and Rhizopus rot (Rhizopus sp.). The
production of disease free peaches in this region is dependent upon the selection
of effective fungicides and proper timing of their applications.
Maygold peach trees planted in February 1964 and 1965, were sprayed with 6
applications of dilute sprays applied by hand gun at 450 p.s.i. The first was
a dormant spray of liquid lime-sulphur, 6 gal/100 gal, of water applied before
bud break (Feb. 20). This spray was used in half of all treatments. The dormant
spray was followed by fungicide and insecticide spray applications on March 27
(shuck split), April 7, April 17, May 5, and May 15. Parathion 1 lb/50 gal. was
used in the March through May spray applications to control insects.
Six fungicides in various combinations with nine, one-tree replications for
each treatment were used. Data from the two age classes (3rd and 4th leaf) were
grouped, and the results summarized in Table I. The monthly rainfall was as
follows: March 2.77; April 0.99; May 6.95; June 1-15, 5.72.
The fungicides tested were: Captan 50W (N-[(trichloromethyl) thio]-4-
cyclohexene-l,2-dicarboximide) 2 lbs/100; Cyprex 65W (dodecylguanidine acetate) +
Captan 50W, 1/2 lb. + 1 lb/100; Difolitan 80W (cis-N-E(l,l,2,2-tetrachlorcethyl)
thio]-4cyclohexene-l,2dicarboximide) 1 lb/100; sulphur W. P. 6 lb/100; dormant
lime sulphur 6 lb/100. Botran 75W (2,6-dichlcro-4-nitro-aniline) 1 1/2 lb/100
was used on half the trees of each treatment in the last application.
1Assistant Plant Pathologist
2The writer wishes to acknowledge J. R. Large, Assoc. Plant Pathologist Emeritus,
for designing and executing the experiment and Dr. Harold W. Young, Assoc, Horti-
culturist and Head, for collecting the data.
Peach leaf curl, bacterial spot and rust were of minor importance on sprayed
and unsprayed foliage this season. Scab was moderate (12.5%) on fruit of un-
sprayed trees. No fruit scab was found on trees sprayed with dormant lime-sulphur
followed with combinations of: Captan + Botran; Difolitan + Botran; sulphur +
Botran; Cyprex + Captan + Botran; nor on trees sprayed with Captan + Botran;
Cyprex + Captan + Bctran; Difolitan + Botran; or Difolitan.
Scab was more severe (25%) on fruit sprayed with liquid lime-sulphur applied
as a dormant spray than on unsprayed trees (12.5%).
CONTROL OF STORAGE DISEASES
Peaches, 20 per tree, (180 per spray treatment) were stored at 75% F. for 4
and 7 days.
The percent of fruits infected after four and seven days is recorded in
Fruit rots caused by Monilinia fructicola and Rhizopus sp. were severe and
generally more than 20 percent after 4 days storage at 750 F. The best disease
control after 4 days of storage was obtained with: Difolitan (90.5%); dormant +
Difolitan + Botran (90.0%); Difolitan + Botran (89.0%); Captan (88.5%); and
Captan + Botran (88.5%). The least effective fungicides were dormant + Botran
(40.0%); dormant + sulphur + Botran (58.0%); dormant only (63.5%); and dormant +
Cyprex + Captan (65.5%).
Fruit infection by Monolinia fructicola on unsprayed peaches was 7.5% after
4 and 7 days in storage while Rhizopus sp. caused 23.0% and 66.0% infection after
4 and 7 days storage respectively.
The most effective disease control after 7 days storage was obtained with:
Cyprex + Captan + Botran (78.0%); dormant + Difolitan + Botran (70.0%); dormant +
Cyprex + Captan + Botran (65.0%); Captan + Botran (63.0%).
Brown rot infections were substantially higher when liquid lime-sulphur
dormant sprays were followed by applications of: Cyprex + Captan; Captan + Botran;
and sulphur + Botran. Rhizopus rot was most severe when liquid lime-sulphur
dormant sprays were followed by applications of Captan + Botran; and sulphur +
The addition of Botran in the last spray application reduced the effective-
ness of Captan in controlling Rhizopus rot. Generally, Botran when added to the
last spray application was not effective in reducing the percentage of brown rot
or Rhizopus rot after four days storage, however, it was effective in reducing
the percentage of Rhizopus rot after seven days storage.
Because of late flowering in some 3rd leaf trees, early applications of
sulphur sprays did not give complete control of scab.
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