We received several samples of squash plants in the last 2 weeks with bacterial disease, either bacterial spot or angular leaf spot. With the rainy weather in many parts of the region, we can expect to see more bacterial diseases on cucurbits and other vegetable crops. On squash, pumpkins, cucumber and other cucurbits, symptoms are typically necrotic spots, sometimes surrounded by a yellow halo. In the morning or after a rain, water-soaked spots may be observed on the leaves. If unsure, contact the OSU Vegetable Pathology lab to send us a plant sample for confirmation.
Unfortunately, once bacterial diseases become established in the field, they are very difficult to manage. Traditionally fixed copper products have been applied, but their efficacy is generally low; many bacterial pathogens are insensitive to some degree to copper. The plant activator Actigard may be applied at 0.5 to 1 oz per acre, and may provide some control.
Squash angular leaf spot