Efficacy of Ethanol in Postharvest Benomyl-DCNA Treatments for Control of Brown Rot of Peach. A. Feliciano, Plant Pathologist, EMBRAPA/CNPFT, Caixa Postal 403, Pelotas 96100, Rio Grande do Sul, Brazil. A. J. Feliciano, J. Vendrusculo, J. E. Adaskaveg, and J. M. Ogawa. Plant Breeder, Food Technologist, EMBRAPA/CNPFT, Caixa Postal 403, Pelotas 96100, Rio Grande do Sul, Brazil; Research Plant Pathologist, and Professor, Department of Plant Pathology, University of California, Davis 95616. Plant Dis. 76:226-229. Accepted for publication 25 September 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0226.

Ethanol at concentrations ?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 ≤ 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 ≥ 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 ≤ 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 ≤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 ≤0.54 μg/ml for benomyl and ≤ 0.29 ?g/ml for DCNA; in the peach syrup, differences between treatments were ≤ 0.36 ?g/ml for benomyl and ?0.11 ?g/ml for DCNA residues.

Keyword(s): disease control, postharvest disease.