Anthracnose

• Sunken, circular, dark-colored lesions on fruit — typically appearing as fruit ripens
• Lesions may have salmon-pink or orange spore masses in the center in humid conditions
• On tomatoes, spots are water-soaked at first, then turn dark and sunken
• Cucumbers and peppers develop similar dark, sunken fruit rot
• Leaves may show small, dark spots but fruit damage is usually most dramatic

Colletotrichum spp. overwinter in infected plant debris and soil. Spores are dispersed by water splash, tools, and insects. Infection can occur on green fruit but lesions typically appear as fruit ripens. Warm temperatures (75-85°F) and frequent rainfall favor outbreaks. The fungus can also infect seed, so using certified disease-free seed is a meaningful prevention step.

1. 01Mulch heavily to reduce soil splash onto fruit
2. 02Avoid overhead irrigation; water at the base of plants
3. 03Stake or cage tomatoes to keep fruit off the ground
4. 04Harvest frequently — fruit left to over-ripen on the vine is more susceptible
5. 05Apply copper-based fungicide preventively when warm, wet conditions persist
6. 06Rotate crops out of affected beds for two to three years
7. 07Use disease-free or certified seed; treat seed with hot water before planting if anthracnose has been a recurring issue

If anthracnose is consistently ruining ripe tomatoes or cucumbers at harvest, an extension office can advise on the most locally effective fungicide program and confirm whether the issue is Colletotrichum or a bacterial soft rot that would require a different approach.

• Anthracnose of Tomato— University of Minnesota Extension
• Anthracnose— Clemson Cooperative Extension