Bean anthracnose

Colletotrichum lindemuthianum is a devastating fungal pathogen responsible for anthracnose in bean crops. Systematically, it belongs to the kingdom Fungi, class Sordariomycetes, and order Glomerellales. As a hemibiotrophic organism, it initiates infection by colonizing living host tissues before switching to a necrotrophic phase that kills the plant cells.

The pathogen primarily attacks common beans (Phaseolus vulgaris). Symptoms appear as dark, sunken lesions on stems, leaves, pods, and seeds. In humid conditions, these lesions produce abundant masses of conidia, which appear as pink or salmon-colored gelatinous pustules. This is a diagnostic feature used for identifying the disease in the field.

The life cycle of the pathogen is closely tied to moisture. It survives between seasons as mycelium in infested seeds or crop debris. Primary infection starts when conidia or mycelia from infected seeds invade the germinating seedling. Secondary spread occurs through rain splash, wind-blown droplets, or mechanical movement of contaminated soil and tools.

Development is highly favored by cool to moderate temperatures (15–22°C) and persistent high humidity. These conditions allow the fungus to produce multiple cycles of spores during a single growing season. Prolonged leaf wetness is critical for spore germination and successful penetration of the plant cuticle by the fungus.

Economic damage includes reduced crop yield, seed discoloration, and complete loss of marketability for fresh beans. Integrated Pest Management (IPM) is essential for control, focusing on using disease-free certified seeds, rotating crops to non-host species for 2–3 years, and applying fungicides when weather conditions suggest a high risk of infection.

• Planting resistant or tolerant cultivars.
• Using high-quality, fungicide-treated seeds.
• Avoiding irrigation systems that wet the foliage.
• Deep plowing to bury crop residues after harvest.