Net blotch on winter barley

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.    

Symptoms of net blotch (Pyrenophora teres) appeared in a campus research plot and a grower’s field of winter barley in Ingham County this week. The foliage had numerous small dark green to light brown spots, and some larger parallel brown stripes and blotches with yellow halos. (see photo) Wheat is not affected by net blotch.

Although there is relatively little barley grown in Michigan, this fungal disease is common wherever barley is grown. As symptoms advance, stripes get larger and can expend the length of the leaf. Lesions can cover and kill entire leaves if disease is severe. Disease may also infect the barley kernels. The fungus spreads mainly from barley residue and volunteer barley plants, but can be transmitted on seed. The disease is favored by windy conditions, high humidity and temperatures in the 60°F to 80°F range. If infected seeds are planted, emerging shoots can be infected after the seeds germinate. Prevention is the best way to deal with net blotch, including crop rotation, removal of crop residue and volunteer plants using resistant varieties and starting with clean seed. If infection has already taken place, there are several fungicides labeled for net blotch.

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