Back to Diseases of cucurbits
Anthracnose is caused by the fungus, Colletotrichum orbiculare. This pathogen can attack all cucurbits but the most severe disease is seen on cucumbers, muskmelons, and watermelons.
All above ground plant parts can be infected. Symptoms vary depending on which cucurbit is infected.
- Irregular brown leaf spots form on squash, melon and cucumber. The center of the leaf spot may drop out resulting in shot hole or ragged appearance. This is most common on cucumbers.
- Cucumber leaf spots often have a yellow halo.
- Watermelon leaf spots are smaller and dark brown to black.
- Sunken elongate stem infections can occur on cucumber and melon, but are not common on other cucurbits. Infections on melon often exude a reddish gum.
- Fruit infections are sunken black spots 1/4 -1/2 inch across and 1/4 inch deep. Spots may have fluffy white cotton like mycelia and sticky salmon colored spores during wet weather.
The Anthracnose fungus can survive in infected plant debris, in and on the seed. Spores are produced on infected leaves and fruit. These are easily spread by splashing rain, irrigation, on workers hands or equipment. The disease is favored by warm, moist environmental conditions and often is first seen mid to late season after the canopy closes. During wet summers, disease can be quite severe.
- Purchase clean seed from a reputable source. Do not save seed from infected plants.
- Some resistant varieties of cucumber are available.
- Rotate vegetables so 3 years go by before planting any member of the squash family in the same location.
- Use drip irrigation instead of overhead sprinklers if possible.
- Do not work in plants when wet.
- Remove and destroy infected vines at the end of the season in small gardens.
- In large fields till under crop residue at the end of the season.
- Several fungicides are registered for use against Anthracnose but may not provide adequate control if good coverage of fruit and leaves is not achieved. Commercial growers should refer to the Midwest Vegetable Production Guide for specific fungicide recommendations.