Cylindrocladium black rot

Cylindrocladium black rot is a severe fungal disease caused by the pathogen Cylindrocladium crotalariae (also classified as Calonectria ilicicola). As a soil-borne pathogen, it primarily attacks the roots and lower stems of host plants, disrupting vascular integrity and leading to plant decay and death.

The disease is most notably recognized as a major threat to peanut crops. The fungus survives in the soil for extended periods due to the production of microsclerotia—small, dark, resilient structures that can withstand extreme environmental conditions and persist in the absence of a host plant for several years.

Symptoms typically begin with the yellowing of foliage and wilting during the day, which becomes permanent as the root system rots. Upon examination, the taproot and lateral roots show black, decaying lesions. In later stages, the stem base exhibits a distinct black discoloration, often covered with a layer of fungal spores.

Development and spread of the pathogen are favored by wet, warm soil conditions. Because the fungus is soil-borne, it moves across fields primarily via contaminated soil on machinery, equipment, farm tools, and through surface water runoff. Infected seeds may also serve as a vector for introducing the disease to new, clean planting areas.

Managing Cylindrocladium black rot requires an integrated approach to break the disease cycle and limit the inoculum buildup:

• implementing long-term crop rotation schemes avoiding susceptible hosts;
• using certified, disease-free seed and applying appropriate seed treatments;
• optimizing field drainage to prevent waterlogging;
• thoroughly cleaning equipment to avoid cross-contamination between fields;
• utilizing resistant peanut varieties whenever they are available.