Control of Botrytis Bunch Rot of Ripening Grapes: Timing Applications of the Dicarboximide Fungicides

Abstract

Various dicarboximide fungicides at 0.84 kg to 1.12 kg (active ingredient)/ha when applied first at 5° to 7° Brix and then two weeks later, provided a high level of control of Botrytis bunch rot (<i>Botrytis cinerea</i> Pers.) of ripening grapes in New York State. Control was rarely improved by making two additional applications at 5% or 90% bloom and at bunch closing. Control provided by two late season applications of vinclozolin was improved significantly when an early season treatment of gibberellic acid at 25 mg/L was included. The use of only two sprays per season may lessen the selective pressure by these fungicides and thereby delay development of fungicide-resistant strains.