Attacks most cucurbits in warm, wet weather. Infected fruit develops circular brown to black sunken areas, up to 1" across. Spores overwinter in and on seed. Cucumber beetles and splashing water spread spores.
For best control, begin spraying with a copper soap fungicide before the disease normally appears (typically when warm, humid weather begins). Repeat application at 7- to 10-day intervals, more frequently if the amount of disease is increasing rapidly. Control cucumber beetles with our Super-Light Insect Barriers or kaolin clay. We recommend Soap-Shield Flowable Liquid Copper Fungicide and Surround At Home Crop Protectant.