Net blotch is a common leaf disease found in barley growing regions across Canada. The disease infects leaves, leaf sheaths and heads. The more severe the infection is to the upper leaves and heads, the greater the crop loss. The disease may appear in two forms, netted net blotch and spotted net blotch. The fungus overwinters on crop residue or seed. Rain and wind will spread the infection from the residue. High humidity and warm temperatures favour disease development.
Symptoms appear on leaves, sheaths and glumes. Early symptoms appear as light green blotches or brown spots on leaves; these enlarge into longitudinal brown streaks, net-like in appearance. The streaks may be surrounded by a yellowish or chlorotic border.
Net blotch may develop only as brown spots and be easily confused with symptoms of spot blotch.
Choose more resistant cultivars (especially 6-row varieties) where available. Seed treatment can reduce incidence of seedling blight. In crop rotation, avoid barley on barley. Apply a foliar fungicide.