Anthracnose Management in Beans, Cucurbits, and Stone Fruit

Anthracnose diseases are caused by species of Colletotrichum and Glomerella fungi. They affect a wide range of crops including beans (C. lindemuthianum), cucurbits (C. orbiculare), avocado (C. gloeosporioides), stone fruit, and many others. Anthracnose is particularly devastating in warm, wet, or humid conditions.

Identification

On leaves: Dark brown angular spots, often with a yellow halo. In humid conditions, acervuli (fruiting bodies) appear as salmon-pink spore masses.

On pods/fruit: Sunken, dark, circular lesions that expand rapidly. Under humid conditions, pink-orange spore masses are visible in lesion centres. Lesions often penetrate into the fruit flesh.

On stems and petioles: Dark cankers and streaks, which can girdle the stem and kill the plant above.

Disease Spread

Colletotrichum spores are spread by:

• •Rain splash
• •Insects
• •Contaminated seed (seed-borne inoculum)
• •Wind in some species

Disease is most severe in temperatures of 20–28°C with prolonged leaf wetness.

Chemical Control

Application Strategy

• •Begin preventive sprays 7–10 days before typical disease onset or at flowering
• •Apply mancozeb or chlorothalonil as the season-long protectant
• •Add systemic products (azoxystrobin, tebuconazole) when conditions are conducive for infection
• •Spray on a 7–10 day interval during wet weather
• •Ensure thorough coverage of leaves, stems, and developing pods/fruit

Seed Treatment

For bean anthracnose: use only certified disease-free seed; treat seed with thiram or mancozeb seed treatment before planting.