TESTING EFFICACY OF HYDROSHIELD PRODUCT ON THE REDUCTION OF ROT AND PHYTOTOXICITY OF EUROPEAN AND FRENCH AMERICAN HYBRID WINE GRAPES IN GEORGIA
Applied Research
Paula Burke
Agricultural & Natural Resources Agent
University of Georgia
Carrollton
Abstract
The objective of this project was to evaluate the effectiveness of the novel, food-grade, agricultural product “HydroShield”, a hydrophobic plant cuticle supplement, to manage the pervasive wine grape rot complex ‘sour rot’. Hydroshield produces a hydrophobic spray film around fruit, preventing water ingress during wetting events (rain or dew). It has also been reported to increase cuticular thickness and decrease spotted wing drosophila (SWD) penetration and oviposition in other commodities. Sour rot is a complex disease; drosophila insects, to include SWD, transmit yeast and acetobacter to damaged grapes where these pathogens establish disease symptoms – producing the equivalent of vinegar in the grapes and rendering them useless for wine production. Decreased drosophila activity in grapes would theoretically result in decreased sour rot. Therefore, two HydroShield formulations were tested for their effectiveness as indirect sour rot management tools in wine grape vineyards in north and west Georgia. Both Hydroshield formulations were applied at a 0.5% v/v rate, calculated to deliver 50 gallons of total spray volume per acre. At each location, five replications of each treatment were applied to a randomized complete block with a CO2 backpack sprayer to runoff. An untreated control was included. Applications were initiated on BB or pea-sized fruit, depending on phenology at project initiation, and were conducted at approximately two-week intervals till shortly before harvest. All other IPM practices were those utilized and provided by the vineyard managers for each site. Test were conducted in Carroll, Fannin, Lumpkin, Union, and White counties. Where observed, sour rot incidence (% infected clusters) and severity (average % damage per cluster) were rated at commercial harvest on all clusters within an experimental unit. Efficacy of Hydroshield against sour rot was not consistently observed. No phytotoxic responses were observed on fruit at any location, but significant leaf damage was observed on Blanc du Bois and Vidal Blanc hybrids, and very minor damage was confirmed on Pinot grisio. Marginal leaf burn was observed with all three varieties where damage occurred, but other symptoms, such as yellowing and bronzing of leaves, was also observed on some varieties.
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Authors: P. J. Burke
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Burke, P. Agricultural & Natural Resources Agent, University of Georgia, Georgia, 30117