Eyespot of sugarcane

Pathogen and disease type. The disease known as eyespot is caused by the fungus Bipolaris sacchari (formerly identified as Helminthosporium sacchari). It is a fungal pathogen that targets the foliage of the host plant, disrupting its normal physiological functions and causing necrotic lesions across the leaves.

Host range. The primary host of this pathogen is sugarcane. While the disease is most severe on commercial sugarcane varieties, the fungus can occasionally survive on various grasses and weed species in the field, which serve as reservoirs for future infection cycles.

Symptoms and signs. The characteristic symptoms manifest as small, red-to-brown spots that elongate along the leaf veins. As the infection progresses, the spots expand and develop a pale yellow or chlorotic halo, giving them a distinct "eye" appearance. In severe cases, these lesions merge, leading to extensive leaf necrosis and premature senescence of the foliage.

Conditions for development and impact. The pathogen thrives in environments characterized by high relative humidity, frequent rain, and temperatures ranging from 20°C to 28°C. Spores are primarily disseminated by wind and splashing raindrops. The economic impact is significant, as the reduction in leaf area directly impairs photosynthesis, leading to lower sugar accumulation and reduced cane yield.

Control and prevention measures. Effective management relies on a combination of cultural and chemical strategies designed to minimize inoculum pressure:

• planting resistant or tolerant sugarcane cultivars;
• ensuring adequate drainage and row spacing to reduce canopy humidity;
• removing diseased plant residues after harvest;
• application of preventative fungicides in high-risk areas;
• maintaining soil fertility to promote vigorous plant growth.