Yellow spot of sugarcane

The causative agent of yellow spot disease in sugarcane is the fungus Passalora koepkei (formerly classified as Cercospora koepkei). It is a specialized fungal pathogen that targets the foliage of the host plant, disrupting its normal development and metabolic processes.

This disease primarily affects sugarcane (Saccharum officinarum) crops. The fungus acts as an obligate parasite, infecting the leaves during various growth stages. The severity of the infection depends on the susceptibility of the specific cultivar and the prevailing environmental conditions throughout the growing season.

Symptoms initially appear as small, yellow, circular to oval spots on the leaf surface. As the infection progresses, these spots expand, change color to brown or dark red, and often show a characteristic yellow halo. Under high humidity, a velvety olive-brown mycelial growth becomes visible on the underside of the leaves, indicating active sporulation.

The spread of Passalora koepkei is highly dependent on climatic factors. High humidity, frequent rainfall, and moderate temperatures provide optimal conditions for the germination of conidia and their dispersal via wind and water splashes. Dense crop canopies that trap moisture are particularly vulnerable to rapid disease development.

The impact of the disease on agricultural productivity is significant, primarily due to the loss of functional leaf area, which reduces the rate of photosynthesis. This leads to diminished sucrose accumulation and lower total cane yield. Effective management involves:

• planting resistant cultivars;
• ensuring adequate crop spacing for better airflow;
• applying fungicides during periods of high disease pressure;
• sanitizing fields by removing infected crop debris.