Problem: Scab (Cucurbits)
This plant disease is caused by a fungus (Cladosporium cucumerinum) that attacks cucumbers, squash, and muskmelons. All parts above ground are affected. Fruit is attacked at all stages of growth, but young fruit is most susceptible. The disease is most prevalent in foggy weather with a daytime temperature range of 60° to 65°F and with temperatures falling below 60°F for several nights in a row. The fungal spores spend the winter in diseased plant debris left in the garden and on seeds.
At the first sign of the disease, treat plants with a fungicide labeled for scab, following label directions. Clean up and destroy plant debris after harvest. Rotate your cucurbit planting site every year, and grow resistant varieties.