Impact of Vine Shelter Use on Development of Grape Powdery Mildew

Abstract

Heavy infection of powdery mildew, Uncinula necator, on grapevines was observed in conjunction with vine shelter use during the 1997 growing season in the Oregon Willamette Valley. The influence of vine shelter use on the development of powdery mildew was investigated in the field during the 1998 and 1999 growing seasons. Installations of vine shelters were examined for both incidence and severity of U. necator infection. Five brands and four installation types were examined. There were no significant differences among brands of vine shelters. The industry standard installation of 76 cm high tubes, hilled with 7.6 cm of soil at the bottom to prevent airflow, resulted in significantly lower incidence of powdery mildew in both field seasons. Significantly increased disease incidence was observed in installations designed to increase airflow in the shelters. Reduction in incidence of disease on leaves was significantly correlated with prolonged temperatures above 36°C within the vine shelters. Vine length was significantly increased depending on shelter brand and installation type in both years.