Eyespot

Eyespot (caused by the pathogen Oculimacula yallundae, formerly Gomphus yallundae or Cercosporella herpotrichoides) is a significant fungal disease affecting primarily winter cereals. This disease belongs to the group of foot rot or basal stem rot conditions, causing severe weakness and lodging in mature stalks.

The primary crops susceptible to this disease include wheat, barley, rye, and triticale. The fungus infects the base of the stems by invading the leaf sheaths, which disrupts the vascular tissues of the plant, leading to nutrient deprivation and premature senescence or lodging.

Initial symptoms are visible in early spring as oval-shaped lesions with a dark border, often referred to as "eyespot" lesions, found on the lower leaf sheaths. Over time, the affected stem tissue softens and weakens, causing the stem to collapse or break easily, which creates an uneven, tangled appearance in the field.

The development of the fungus is favored by high humidity and cool, damp weather conditions during the tillering stage of the cereals. The pathogen survives in the soil and on crop debris, meaning that the risk of infection significantly increases in fields with continuous monocropping of susceptible cereal species.

The economic impact of eyespot is substantial, as it leads to reduced grain weight, poor grain quality, and lodging, which complicates mechanical harvesting. Effective management practices include implementing proper crop rotation, planting resistant varieties, and applying fungicides during the stem elongation stage to mitigate spread.