Anthracnose of Cucurbit Crops
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Anthracnose (Colletotrichum orbiculare) is most common on cucumber, muskmelon, gourds, and watermelon. It may occur on squash and pumpkin. All aboveground plant parts can be affected. Small, circular lesions develop initially on leaves. These lesions enlarge to form large tan to brown spots that may coalesce to create extensive blighting. On watermelon, leaf lesions tend to be smaller, irregularly shaped, and darker in color. The centers of older lesions may crack or fall out entirely. Lesions on stems are tan-brown, somewhat elongated, and sunken. On maturing fruit, lesions appear as small, circular, sunken areas. Lesions may grow to the size of a quarter or larger on melons. Lesions on watermelon can be cracked and irregularly shaped. Under humid conditions, lesions will blacken and salmon-pink masses of spores may be seen.
Anthracnose on melon fruit.
(Photo: Kenny Seebold, University of Kentucky)
Anthracnose on melon fruit.
(Photo: Kenny Seebold, University of Kentucky)
Anthracnose on foliage.
(Photo: Kenny Seebold, University of Kentucky)
Management:
- Pathogen-free seed
- Planting of resistant varieties (watermelon—races 1 and 3; cucumber—races 1, 2, and 3)
- Crop rotation
- Sanitation (debris removal)
- Irrigation management (avoid overhead irrigation where possible)
- Fungicides
