Apr 15, For melon growers, a few of the top diseases to be on the lookout for this season include Fusarium wilt, angular leaf spot, and powdery mildew. Watermelon, Citrullus lanatus, is a vining annual plant in the family Cucurbitaceae grown . fungicides are usually required to control the disease successfully. See: UC Pest Management Guidelines Fusarium Wilt (Watermelon). Fusarium Wilt on Melons. Anthracnose. Anthracnose is a Very destructive disease of.