Northern anthracnose of clover

Pathogen and disease type. Northern anthracnose is a fungal disease caused by the pathogen Aureobasidium caulivorum. It is a specialized parasite that primarily affects the stems and petioles of its host plants. By disrupting the vascular integrity of the plant, the fungus prevents the proper transport of nutrients, leading to systemic weakness of the crop.

Affected crops. The disease primarily targets red clover (Trifolium pratense). As a crucial forage legume, red clover is particularly susceptible during periods of rapid vegetative growth. While other legumes may be present in the field, the pathogen shows a distinct preference for Trifolium species, making it a significant concern for agricultural producers specializing in dairy and livestock feed.

Symptoms and signs. The characteristic symptoms include dark, elongated lesions or streaks on the stems and leaf stalks. These lesions often girdle the stem, causing it to wilt, collapse, or break off entirely. Under humid conditions, the pathogen may produce visible fungal structures within these lesions. As the infection progresses, the affected tissue turns brown and eventually dries out, leading to plant death.

Conditions for development and spread. The fungus thrives in cool, moist weather conditions, which are typical for late spring and early autumn. Rain splashes and wind play a major role in the dissemination of spores from infected debris to healthy plants. High plant density and frequent rainfall create an ideal microclimate for the pathogen to establish and rapidly expand across the field.

Protection and prevention measures. Controlling Northern anthracnose requires a proactive agronomic strategy.

• Crop rotation is essential, with a minimum 3-year break from clover.
• Selecting resistant or tolerant clover cultivars is the most effective management tool.
• Field sanitation, including the removal of crop residues, helps reduce inoculum.
• Optimizing soil fertility to ensure vigorous plant growth.
• Avoiding excessive nitrogen levels, which can make tissues more succulent and prone to infection.