University of Florida, IFAS
Southwest Florida Res. And Ed. Center
P. D. Roberts and R. E. Systma
Objective: Evaluate under guidelines established by the University of Florida/IFAS for
land preparation, fertility, weed management and insect control, the control of foliar diseases
(Gummy Stem Blight; Didymella byyoniae), at the Immokalee, FL Research Center.
Method: Watermelon transplants were transplanted to the field on 7 March into Immokalee fine sand.
Each plot consisted of 10 plants spaced 36 in. apart with 10 ft. between plots. All compounds were applied
with a backpack CO2 sprayer at 40 psi with a single hollow-cone nozzle at 24 gal/A. Two isolates of the
Didymella byyoniae were obtained from S. Semer, Gainesville, FL. The spore suspension was applied with a
hand pump to all plants in plots on 18 April. Fruit were rated as marketable or non-marketable (small,
misshapen or diseased).
Results: Disease pressure for gummy stem was severe: the control plants were dead on the final
reading date (10 May). Symptoms of gummy stem were significantly reduced by most application treatments
except 9, 10 and 12 programs. No differences in the number of marketable number of fruit were detected
although some treatments such as the untreated control and treatment 14 had significantly reduced weight
of marketable yield.