Phytophthora blight, caused by Phytophthora capsici, is one of the most serious threats to production of cucurbit crops (cucumbers, melons, pumpkins, and squash) in Illinois and many other cucurbit growing areas in the United States, as well as in the world. Phytophthora blight also affects eggplants, peppers, tomatoes, and more than 40 species in 15 plant families. In recent years, Phytophthora blight occurred widely in Illinois, causing yield losses up to 100% in cucumber, cantaloupe, jack-o-lantern pumpkin, processing pumpkin, squash, and watermelon fields (Figure. 1).