Abstract
Kaolin clay particle films offer multiple uses for managing pests and abiotic stress in horticultural cropping systems. Kaolin clay can specifically benefit wine grape production, but this potential is underexplored in the United States. This study addresses two issues for wine grape producers in the Columbia Basin: western grape leafhopper (
Erythroneura elegantula
Osborn) populations and fruit sunburn damage. Two experiments were established in vineyards near Milton-Freewater, OR, USA: one in an organic Cabernet Sauvignon block with established leafhopper populations and another in blocks of Mourvèdre, Syrah, and Tempranillo. In the first experiment, kaolin was applied to whole canopies of Cabernet Sauvignon vines, and leafhopper populations were monitored weekly. Kaolin application reduced the peak abundance of second-generation leafhopper nymphs by 54% to 80%, although abundances were relatively low compared with other reports. Kaolin application did not influence Cabernet Sauvignon fruit quality. In the second experiment, west side basal leaves were removed and kaolin was applied to clusters before forecasted multiday extreme heat events (>100 °F). Clusters were rated for sunburn damage (i.e., berry shrivel, browning, and necrosis) following the heat events. The efficacy of kaolin varied by cultivar and year but generally reduced sunburn damage and improved the concentration of berry anthocyanins. While kaolin application did not eliminate sunburn damage, it proved an effective tool to reduce loss of usable fruit and improve quality of fruit exposed to both high temperature and light conditions. These experiments validate two important kaolin applications in vineyards under the warm climate conditions of the Columbia Basin region. As insect pest pressures and the frequency of extreme heat events increase, this technology is a critical tool for adapting perennial crops like grapes to a changing climate.