Eyespot disease

Eyespot disease, caused by the fungus Pseudocercosporella herpotrichoides (recently reclassified as Oculimacula yallundae), is a major root and stem disease affecting small grain cereals. It primarily attacks the base of the stem, interfering with the plant's vascular system and weakening its physical structure.

Winter wheat, winter barley, and rye are the most susceptible crops. The fungus survives as mycelium in infected stubble and soil debris. During cool, wet conditions, it produces spores that are splashed by rain onto the lower parts of young cereal plants, initiating the infection process during the autumn or early spring.

Symptoms initially appear as diffuse brown spots on the leaf sheaths. As the disease progresses, a distinct lesion develops on the stem at the base of the plant. This lesion is often oval or lens-shaped with a dark brown border and a lighter center, which is why it is commonly referred to as an "eyespot". Severe infections cause the stem to soften and collapse, leading to lodging.

The development of the disease is heavily dependent on the climate. Cool temperatures (around 5°C to 15°C) and persistent high humidity are essential for the fungus to spread. Early planting of winter cereals and high plant density create a microclimate that traps moisture, significantly increasing the risk of an eyespot outbreak in the field.

Management strategies focus on reducing the pathogen inoculum and strengthening the crop:

• Implementing crop rotation cycles to break the infection chain.
• Using resistant cereal cultivars to prevent rapid disease spread.
• Delaying autumn sowing dates to reduce early exposure to spores.
• Avoiding excessive nitrogen fertilizer applications which increase canopy density.
• Applying fungicides during the stem elongation stage if the disease threshold is met.