Sharp eyespot

Sharp eyespot is a fungal disease caused by the soil-borne pathogen Rhizoctonia cerealis. As a saprotrophic fungus, it persists in soil and crop debris, switching to a parasitic phase when environmental conditions favor colonization of the crown and base of host plants.

The primary hosts for this pathogen are small grain cereals, specifically wheat, barley, rye, and oats. The fungus exhibits a broad host range, meaning it can survive on various grass species and cereal stubble, which makes disease management challenging in short-rotation cropping systems.

Symptoms are typically observed on the lower leaf sheaths and internodes during the spring. The disease is characterized by distinct, eye-shaped lesions with a pale center and a dark, sharp brown margin. Severe infections weaken the stem base, often leading to lodging, whitehead formation, and a significant reduction in grain filling.

The development of Rhizoctonia cerealis is highly dependent on environmental factors, particularly moisture and temperature. Cool, damp conditions during autumn or spring facilitate the infection process. The fungus survives as mycelium or sclerotia in the soil, spreading through water splashes and direct contact between the fungus and plant tissues.

The economic impact of sharp eyespot is significant, as the pathogen restricts nutrient transport by damaging the stem vascular system. Affected crops show reduced tillering and overall biomass, leading to yield losses of up to 20% in severe cases. Furthermore, grain quality and marketability are often compromised by shriveled kernels.

• Implementing diverse crop rotations to reduce inoculum levels in the soil.
• Managing crop residues through appropriate tillage to promote decomposition.
• Treating seeds with effective fungicides to protect seedlings during germination.
• Optimizing seeding rates to prevent dense canopies that increase local humidity.
• Scouting fields during early growth stages and applying registered fungicides when thresholds are met.