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Effects of Spray Adjuvants on Development of Botrytis cinerea on Vitis vinifera Berries. J. J. Marois, Department of Plant Pathology, University of California, Davis 95616; A. M. Bledsoe, R. M. Bostock, and W. D. Gubler. Department of Plant Pathology, University of California, Davis 95616. Phytopathology 77:1148-1152. Accepted for publication 10 February 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1148.

Ten agricultural spray adjuvants, including spreaders, stickers, and a penetrator, were sprayed on mature grape berries (cultivar Thompson Seedless or Emperor) at 0.125% product. Twenty microliters of a suspension of conidia of Botrytis cinerea containing 2 104/ml was applied to the surface of each berry after the berries dried. Water and chloroform treatments were used as controls. The overall mean of disease incidence and slope of disease increase over time were increased significantly by the treatments, with the chloroform treatment being affected most. Application of Penetrator 3 actually reduced the slope of the disease increase. The effects of Triton B1956, Ortho X-77, and Penetrator 3 on spore germination, sugar exudation, and berry water uptake and loss were studied. Germination of conidia increased significantly in the water droplets on the treated berries or when the water droplets were removed after 6 hr and the conidia added. The rate of exudation of reducing sugars was not affected significantly by the adjuvants; however, the rate of water uptake and loss by treated berries was increased, indicating that the epicuticular wax was affected by the spray adjuvants.

Additional keywords: resistance, surfactants.