Fungicide Efficacy and Specificity Toward Fungi in the Cranberry Fruit Rot Disease Complex

Abstract

Cranberry fruit rot is an economically important disease complex comprised of as many as 15 different fungi that destroy cranberries in the field and/or after harvest. We evaluated fungicides in six field trials over 3 years for their ability to reduce the incidence of cranberry fruit rot and for their specificity in controlling six principal pathogens in the complex: Coleophoma empetri, Colletotrichum acutatum, Colletotrichum gloeosporioides, Phomopsis vaccinii, Phyllosticta vaccinii, and Physalospora vaccinii. Fruit rot incidence and efficacy of fungicides varied greatly among replicate plots within trials and among trials, often making it difficult to discern significant differences among treatments. However, in general, the newer strobilurin and sterol demethylation inhibitor (DMI) fungicides were at least as effective as the industry standards, chlorothalonil and mancozeb. An exception was the DMI fungicide fenbuconazole, which was ineffective in three of five trials. Compared to other fungicides, fenbuconazole was weak in controlling Colletotrichum gloeosporioides, which along with Coleophoma empetri, dominated among fungi isolated from rotten berries. The results are being used to develop disease management programs that control the key fruit rot pathogens with reduced reliance on environmentally risky and potentially carcinogenic fungicides. Accepted for publication 21 January 2014. Published 14 March 2014.