Rhynchosporium scald

Rhynchosporium scald, caused by the fungus Rhynchosporium secalis, is a major fungal disease affecting small grain cereals, particularly barley and rye. It is a worldwide problem in temperate regions, frequently causing significant yield losses by reducing the photosynthetic capacity of the plant leaves.

The pathogen primarily infects the leaf blades and sheaths, although in severe cases, it can spread to the stem and ear parts. The disease is most damaging during the early growth stages of the crop, especially when cool and wet weather conditions persist for an extended period.

Symptoms are distinct and easily identifiable: they appear as water-soaked, grey-green lesions that rapidly expand into characteristic oval or lens-shaped spots. As the lesions age, the center turns pale grey or white, bordered by a dark brown or blackish margin, which often creates a mottled appearance on the leaf surface.

The fungus survives on infected crop debris, volunteer plants, and contaminated seed. During the growing season, conidia are dispersed by rain splashes and wind. Optimal conditions for disease development include high humidity, leaf wetness, and temperatures between 15°C and 20°C, which favor the spread of the pathogen.

Effective management strategies are essential to minimize economic impact. These include:

• planting resistant or tolerant cereal cultivars;
• utilizing crop rotation to break the life cycle of the pathogen;
• managing crop residues through tillage;
• applying registered fungicides, such as triazoles or SDHIs, when weather conditions favor outbreaks.