Most foliar diseases are spread by water-splash or are favored by long periods of leaf wetness. Use drip irrigation or avoid frequent sprinkler irrigation with small amounts of water. Finally, use tillage practices that promote the rapid decomposition of old vines and melons soon after harvest. The use of disease-resistant varieties is an economical means of controlling diseases. Several varieties have resistance to Fusarium wilt.
Some varieties also are resistant to anthracnose.
Management of foliar diseases such as anthracnose, downy mildew, Cercospora leaf spot, and gummy stem blight may require fungicide sprays. Consult North Carolina Agricultural Chemicals Manual for a listing of fungicides approved for use on watermelon Around the world, over 10 viruses are known to be a problem in watermelon production. Virus diseases are destructive to the watermelon crop, and are difficult to control. The major control strategies involve insecticides to eliminate the insect vectors, herbicides to remove alternate hosts, or genetic resistance. The most economical method for control of virus diseases is genetic resistance.