How to Manage Pests
UC Pest Management Guidelines
Pathogen: Colletotrichum lagenarium
(Reviewed 11/05, updated 6/08, pesticides updated 5/16)
In this Guideline:
Symptoms and Signs
In California, anthracnose is unusual on cucurbit crops other than seedless watermelon. It can cause leaf, fruit, and/or stem lesions. Foliage lesions are tan to brown except on watermelon foliage where they are dark brown to black. Fruit may develop brown to black, sunken, water-soaked spots. Tiny, black fruiting structures, called acervuli, form within the lesion. In wet weather, pink or orange spores ooze from these fruiting bodies.
Comments on the Disease
The fungus overwinters on cucurbit plant residue in the soil, on volunteer cucurbits, or on cucurbit seed. Disease development is favored by warm, wet weather. This disease is rarely seen in the field and more often occurs on transplants raised in the greenhouse.
There is resistance in some varieties of watermelon and cucumber, but not in seedless watermelon. Control tactics include crop rotation, use of clean seed, and inspection of transplants. Avoid sprinkler irrigation and keep the tops of the beds dry. Fungicides are rarely needed in California but may be required on seedless watermelons at the first sign of disease.
UC IPM Pest Management Guidelines: Cucurbits
R. M. Davis, Plant Pathology, UC Davis
Acknowledgment for contributions to Diseases:W. D. Gubler, Plant Pathology, UC Davis