EFFICACY OF ETHANOL IN POSTHARVEST BENOMYL-DCNA TREATMENTS FOR CONTROL OF BROWN ROT OF PEACH

Ethanol at concentration greater-than-or-equal-to 30% improved the efficacy of benomyl-DCNA mixtures in 1-min dip treatments for control of postharvest brown rot in peach. The model of the regression analyses was significant (P less-than-or-equal-to 0.01) and linear (r2 = 0.97). The slope of the equation for the incidence of brown rot and the concentration of ethanol with fungicide was similar, but the Y intercept and midpoint values were lower than when ethanol was used alone. Control of brown rot was best with 70% ethanol, but shriveling of fruit epidermis from dehydration was greatest at this concentration. Addition of 30% ethanol to a benomyl-DCNA mixture reduced disease incidence and fungal sporulation after 6 days of incubation. Fruit were commercially acceptable, with only limited dehydration. Slopes of each linear equation were similar (P greater-than-or-equal-to 0.05) for 0.5-, 1.0-, and 2.0-min dipping periods as related to the incidence of brown rot and the concentration of ethanol (0, 30, 50, or 70%) in a benomyl-DCNA mixture. The incidence of brown rot vs. dipping time (5, 10, 20, and 30 sec) in a benomyl-DCNA mixture suspended in 30% ethanol was significant (P less-than-or-equal-to 0.05) and linear (r2 = 0.92). Less disease accompanied longer dipping periods. When fruit were inoculated with conidia of Monilinia fructicola and incubated for 4-48 hr before being dipped in a benomyl-DCNA mixture suspended in 30% ethanol, lesions after 6 days were smallest in fruit treated less-than-or-equal-to 12 hr after inoculation. The regression of lesion diameter vs. delay of treatment after inoculation was linear (r2 = 0.91). In canned peach flesh, residues between treatments with or without ethanol differed by less-than-or-equal-to 0.54-mu-g/ml for benomyl and less-than-or-equal-to 0.29-mu-g/ml for DCNA; in the peach syrup, differences between treatments were less-than-or-equal-to 0.36-mu-g/ml for benomyl and less-than-or-equal-to 0.11-mu-g/ml for DCNA residues.