Relationships among spread-sticker application, blossom cap retention, berry scarring, thrips populations, and Botrytis bunch rot in 'Chardonnay' grapes, and a survey of pesticide use and pest severity in Virginia vineyards in 1990 and 1991

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Virginia Tech


A field study was conducted in 1991 to determine whether high rates of cap retention in 'Chardonnay' grapes contributed to increased levels of Botrytis bunch rot (Botrytis cinerea Pers.), and whether spreader-sticker application enhanced cap retention. At bloom, the sticker Nu-Film 17®, or water (control), was sprayed onto single clusters at diluted ( 0.63 ml/ L ) and concentrated ( 1.26 ml/L ) label rates. After fruit set, some clusters were cleaned of caps and other flower parts with pressurized air. Cap and debris retention, berry scarring, and Botrytis rot were evaluated throughout the season. The spreader-sticker application increased debris retention only slightly. Removal of caps and debris had no effect on scarring, but reduced Botrytis bunch rot. The role of flower thrips Frankliniella tritici (Fitch) in causing scarring and in increasing Botrytis rot in Chardonnay grapes was explored in 1992. The insecticide methomyl (Lannate®) at a labeled rate (0.9 ml per 377 ml water per vine), or water (control), was sprayed onto selected vines twice at bloom. Berry scarring and Botrytis bunch rot were evaluated at mid-season and at harvest. The insecticide treatment reduced scarring, but did not affect Botrytis rot incidence. A survey of Virginia grape growers was conducted for 1990 and 1991, to collect information on pest and disease severity and chemical and non-chemical pest control methods. In growers’ opinions, black rot, Japanese beetle, and annual grasses were the most severe disease, insect, and weed problems respectively. Pesticides most commonly used were captan, glyphosate, and carbaryl.