Efficacy of fungicide applications and powdery mildew resistance in three pumpkin cultivars

Powdery mildew (Podosphaera xanthii) is a common and major disease of pumpkin (Cucumis pepo) that affects seedlings and mature plants. Powdery mildew primarily grows on the surface of the leaves. Thus, contact fungicides can be effective in controlling the disease. Biofungicides work as contact fungicides and can be effective treatments for the control of powdery mildew. The objective of this study was to determine the efficacy of biofungicide treatments, polyoxin D zinc salt, Bacillus amyloliquefaciens, and copper octanoate, and compare them to a conventional fungicide spray program of chlorothalonil and azoxystrobin. To study the combination of biofungicides and conventional fungicides three pumpkin cultivars were chosen: 'Gold Medal' with no powdery mildew resistance, 'Early Giant' with intermediate powdery mildew resistance, and 'Mustang' with high powdery mildew resistance. The plots were arranged in a split-plot design with four replications. Results indicate that chlorothalonil and azoxystrobin treated plants had less disease, more fruit, and greater fruit yield in all pumpkin cultivars compared to the plants treated with biofungicides. In addition, the pumpkin cultivar 'Mustang' was the healthiest and had greatest yields when compared to 'Early Giant' and “Gold Medal'. The biofungicides in the current study demonstrated minor efficacy.