2018 ASHS Annual Conference

Cucumber and squash are cucurbits that have nutritional and medicinal benefits. These two crops contain essential provitamins, vitamins, and minerals such as potassium, iron, calcium, magnesium, manganese, copper, phosphorous, and calcium. In Tennessee, these cucurbit crops are affected by several major infectious diseases including anthracnose, Cercospora leaf spot, cucumber mosaic, downy mildew, Phytophthora fruit and crown rot, Septoria leaf spot, squash mosaic, Verticillium wilt, and powdery mildew which severely reduce their productivity. Powdery mildew is ranked as the most severe disease of these cucurbits. Symptoms of powdery mildew appear as a white powdery residue on the upper leaf surface with circular patches or spots. Infected leaves become brown and shriveled and defoliate prematurely and infected fruits remain small and do not develop fully. Thus, the yield is reduced due to a decrease in the size or number of fruits and/or a decrease in the length of the harvest period. The purpose of this study is to control/treat powdery mildew in cucumber and squash using Biological Control Agents (BCAs). BCAs are known to reduce disease incidence directly or indirectly by inhibiting the development and activities of pathogens and/or promoting plant growth. The BCA mechanisms of actions include direct antagonism of the pathogens by selectively attacking pathogens through hyper-parasitism, production of antibiotics and/or lytic enzymes, competition for space and food source, and by inducing systemic resistance in the host plants. Our study focuses on evaluating the effect of five previously isolated BCAs in controlling powdery mildew using weekly foliar sprays on cucumber and squash plants. Our preliminary results show a decrease in powdery mildew disease severity after four BCA applications. Extensive analysis of plant growth response to BCA applications is in progress.