Soybean anthracnose

Colletotrichum navitas is a fungal pathogen responsible for causing anthracnose in soybean plants. As a specific member of the Colletotrichum genus, it has evolved to colonize various tissues of the soybean crop, significantly impacting plant health and yield. It is recognized as a major biotic constraint in many soybean-producing regions worldwide.

The primary host for Colletotrichum navitas is soybean. The pathogen can infect the crop at virtually any growth stage, from seedling emergence through pod fill. The fungus survives in crop debris and can also be seed-borne, which allows it to persist in fields even in the absence of a host for a limited period, complicating management strategies.

Symptoms of the disease are characterized by dark, sunken, irregular lesions on stems, petioles, and pods. Small black fruiting bodies, known as acervuli, are typically visible within these lesions and often contain dark setae. Under high humidity conditions, the fungus produces masses of spores that may appear as gelatinous, pinkish or orange droplets on the infected tissue.

Disease development is highly dependent on environmental conditions, particularly moisture. Periods of high humidity and rainfall, combined with temperatures between 20°C and 28°C, are optimal for spore germination and infection. Rain-splash helps disseminate the fungal spores from the lower canopy to the upper parts of the plant, often leading to rapid field-wide outbreaks.

The economic impact of Colletotrichum navitas is significant, as it can cause substantial yield losses due to pod abortion, poor seed fill, and reduced seed quality. Effective management requires an integrated approach.

• Use of disease-free, certified seeds.
• Crop rotation to reduce primary inoculum levels.
• Deep tillage to bury crop residues.
• Application of foliar fungicides at critical growth stages.