Rhynchosporium/Leaf Blotch
Rhynchosporium secalis
Pathogen
Fungus
Hosts
Barley, rye, grasses
Symptoms
The first symptoms are large (1cm) pale green watery oval lesions on the leaf blade. These turn pale brown and develop a darker margin. In severe attacks lesions become crowded and lose their characteristic shape and colour.
Often the first lesions appear near the base of the leaf (water running down the leaf tends to deposit spores in this position). The lesions then develop and can lead to total loss of the leaf. The leaf sheaths and ears can also be infected.
Development
The inoculum for infection comes from previous barley crops, volunteers, seeds and grasses. The disease is spread by rain splash and dew.
Favourable Factors
Cool (10°C to 15°C) and wet weather conditions. Early sowing, susceptible varieties and high rainfall contribute to severe attacks.
Importance
Yield loss up to 40% in severe attacks but more often between 2% and 5% due to a reduction in grain size.
Control
Correct use and mixtures of fungicides during the growing season will give good control
Stubble cleanliness
Correct choice of variety
