Control of Botrytis cinerea on Grape Berries During Postharvest Storage with Reduced Levels of Sulfur Dioxide. J. J. Marois, Department of Plant Pathology, University of California, Davis 95616. A. M. Bledsoe, and W. D. Gubler, Department of Plant Pathology, University of California, Davis 95616, and D. A. Luvisi, Farm Advisor, Bakersfield, CA 93303. Plant Dis. 70:1050-1052. Accepted for publication 8 July 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-1050.

Mature berries of Vitis vinifera ‘Thompson Seedless,’ ‘Flame Seedless,’ or ‘Emperor’ were inoculated with Botrytis cinerea and stored at 0 C for 6 wk. The berries were treated three times a week with 0, 50, 100, 200, 800, or 3,200 ppm of sulfur dioxide. The 200-ppm sulfur dioxide treatment controlled the development and spread of disease in the inoculated berries, but complete control on naturally infected berries was not obtained until 800 ppm of sulfur dioxide was used. Bleaching was not observed on berries treated with 200 ppm sulfur dioxide or less. The 200-ppm rate applied three times a week was tested under commercial storage conditions and compared with the standard practice of 2,500 ppm of sulfur dioxide applied every 7 days. After 10 wk in storage, 30% of the inoculated berries had mycelium of the pathogen on them in the 200-ppm treatment compared with 71.2% in the standard control treatment. Spread from inoculated berries to neighboring berries was 0.65 and 2.35 berries per inoculated berry in the 200-ppm treatment and the standard control, respectively. The 75% reduction in total sulfur dioxide used in the 200-ppm treatment, compared with the standard treatment, reduced bleaching of berries.