Bean Anthracnose
ANTHRACNOSE OF BEAN
Anthracnose, caused by Colletotrichum lindemuthiana, occurs worldwide except in hot dry areas and infects all aerial parts of the plants. The fungus is pathogenic to common bean, scarlet runner bean, mung bean, cowpea, and fava bean. Anthracnose can occur in many different pathogenic strains or races.
Symptoms on leaves consist of angular red brown spots and red brown sections of leaf veins. Stems and petioles develop sunken, elliptical lesions with darker margins. The pathogen can infect the hypocotyl and cause stem collapse when the stem is girdled. Pods also develop sunken, brown lesions and seed can become infected. Affected seed may have yellow or brown lesions, be shriveled, and fail to germinate. Severe infection results in defoliation and pod distortion.
C. lindemuthiana survives in crop residues and in seed. It is disseminated within fields by rain, wind, and splashing water. The disease is favored by cool temperatures, frequent rainfall, and high humidity.
Management
- Resistant cultivars are available.
- Start with certified, disease-free seed or treat seed with fungicides.
- Rotate for 2-3 years with nonhost crops such as cereal or corn.
- Reduce plant density to promote rapid drying of foliage and pods.
- Preventive fungicide sprays have limited effectiveness. If applications are made they should coincide with flower initiation. Registered materials include maneb, chlorothalonil (Bravo), thiophanate-methyl (Topsin), and pyraclostrobin (Headline).
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