Anthracnose

Anthracnose typically appears as sunken, dark brown to black lesions on leaves, stems, pods, or fruit. In humid weather, small fruiting structures called acervuli often develop within the lesions, producing masses of pink to orange, sticky spores that give affected areas a distinctive salmon-coloured sheen. On bean pods, lesions often form dark, sunken cankers; on mango and banana fruit, lesions expand rapidly as fruit ripens.

Colletotrichum species produce spores in acervuli on infected tissue that are dispersed mainly by rain splash over short distances, though infected seed and planting material can move the fungus over long distances. On some hosts, spores can infect young, immature tissue and then remain quiescent, resuming active growth only as the tissue matures or ripens and its natural defences change.

• Survives between seasons in infected crop debris, seed, and, on perennial hosts, in twigs and old lesions
• Warm, wet, or humid weather with splashing rain favours spore release and new infections
• Wounds and natural openings provide additional infection points on some hosts

Anthracnose affects a very wide range of crops through different, largely host-adapted Colletotrichum species. Common bean is affected by pod and leaf lesions that can reduce seed quality; mango and banana suffer serious post-harvest fruit rot; and cucurbits such as cucumber can develop leaf, stem, and fruit lesions in the field.

• Common bean: leaf, pod, and stem lesions that can affect seed quality
• Mango and banana: quiescent fruit infections that develop into rot after harvest
• Cucumber and other cucurbits: leaf spots, stem lesions, and fruit rot

• Warm temperatures combined with rain, dew, or high humidity
• Overhead or splash-prone irrigation that disperses spores
• Infected or untreated seed and planting material
• Dense canopies and poor air circulation
• Rough handling of fruit that creates wounds during and after harvest

Because several Colletotrichum species can establish quiescent infections well before symptoms appear, management emphasises clean planting material, sanitation, and careful post-harvest handling alongside field-level prevention.

• Use certified, disease-free seed and planting material where available
• Choose resistant or tolerant varieties where available
• Remove and destroy infected plant debris and prunings
• Improve air movement through spacing and canopy management
• Handle harvested fruit carefully to minimise wounds and manage post-harvest storage conditions