Grapevine downy mildew control: exploring alternatives to metalaxyl

Abstract

Downy mildew is a debilitating disease of grapevines. In years of excessive rainfall, poorly-controlled infections can decimate the crop and defoliate vines well before harvest, severely hindering fruit ripening and damaging vine health. Effective disease management requires integration of non-chemical vineyard practices and well-timed fungicide sprays. Among the most effective fungicides is metalaxyl, labeled for use on NY grapes since the late 1980's. However, low concentrations of metalaxyl have recently been discovered in Long Island test wells associated with several commodities, including grapes. We explored the activities of recently labeled fungicides to promote alternatives to the use of metalaxyl in vineyards. Though disease pressure was low, all fungicides tested provided good control of downy mildew.