Cowpea anthracnose

The pathogen's life cycle involves the formation of conidial fruiting bodies known as acervuli, which rupture the epidermis of the infected tissue. The fungus has a high capacity for rapid reproduction in high humidity conditions.

The fungal mycelium can persist for a long time in infected plant debris, as well as on the surface or inside the seeds. This makes the planting material a primary reservoir for infection when introduced to new areas.

The pathogenicity of Colletotrichum vignae is driven by the secretion of specific enzymes and toxins that degrade host plant cell walls, facilitating hyphal penetration into tissues.

In the natural environment, the spread of fungal spores occurs primarily through rain splashes, irrigation water flow, and wind that carries conidia to neighboring healthy plants.

Early symptoms of the disease appear as dark brown or nearly black spots with a characteristic light center on cotyledons and leaves of young seedlings. These spots may feature a reddish border.

Deep, elongated ulcers often form on the stems and petioles of infected plants. These lesions frequently lead to stem bending and the death of individual plant parts due to disrupted vascular conductivity.

On pods, anthracnose manifests as circular, sunken spots that, in high humidity, become covered with a pinkish or grayish mold, representing the mass of fungal spores.

If the infection is severe, premature leaf drop occurs, and the grains within the pods become deformed, covered in mold, and lose their viability and commercial quality.

In cases where the root system or the crown area of the stem is affected, general plant stunting, chlorosis of the leaves, and subsequent wilting of the entire vegetative mass are observed.

The development of the pathogen is most intense during warm weather with high relative humidity (above 85–90%). Frequent rainfall significantly promotes the spread of infection across the field.

The optimal temperature for spore germination and tissue infection is between +20 and +25 degrees Celsius. At temperatures below +15 or above +30 degrees, the progression of the disease slows down significantly.

Dense crop stands, where aeration is poor and a microclimate with excessive humidity is created, are the most vulnerable zones for the initiation of anthracnose epiphytotics.

The lack of proper crop rotation, where cowpeas are sown on the same field for several consecutive years, leads to the accumulation of a high inoculum density in the soil.

Imbalanced plant nutrition, particularly excessive nitrogen fertilization, reduces the natural immunity of plants, making them more susceptible to colonization by Colletotrichum vignae.

Cowpea anthracnose causes significant economic losses for agricultural enterprises by substantially reducing bean yields and the quality of the harvested product.

Infection of seedlings leads to mass mortality, requiring replanting and increasing production costs for seeds and soil cultivation.

Damage to generative organs during the flowering and pod-filling phases results in lower grain yield, and damaged pods often become unsuitable for long-term storage.

The disease negatively impacts the photosynthetic activity of plants by damaging the leaf apparatus, which prevents optimal nutrient accumulation and reduces the thousand-grain weight.

Furthermore, seeds harvested from infected plants act as secondary sources of infection, hindering the acquisition of high-quality seed stocks without additional disinfection costs.

The primary control method is the use of healthy seed material that has undergone thorough cleaning and fungicide treatment before sowing to eliminate superficial infection.

Strict adherence to crop rotation, returning legumes to the same field no sooner than every 3–4 years, helps significantly reduce the inoculum pressure in the soil.

Deep plowing of crop residues in the autumn is necessary to accelerate their decomposition and the destruction of the overwintering fungal mycelium.

Upon the appearance of the first disease symptoms in the field, the application of chemical fungicides based on contact and systemic active ingredients effective against Colletotrichum species is recommended.

An important agrotechnical practice is the timely control of weeds that may act as additional disease reservoirs, as well as maintaining optimal planting density to improve plant ventilation.