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. Anthracnose Anthracnose is a very common fungal disease and is caused by the seed-borne fungus Colletotrichum lagenarium .
Most cucurbits are susceptible.
Most commercial watermelon varieties have some resistance. Depending on weather, leaf and fruit spotting may occur on young plants, especially in late plantings. Appears first on crown leaves as small, brown-black spots. During damp weather, orange-pink masses of spores develop in centers of larger leaf spots. During dry weather the spore masses turn gray.