Eyespot of wheat
Eyespot, also called strawbreaker foot rot, can cause yield losses up to 50%. This disease is caused by the pathogens Oculimacula acuformis and O. yallundae. Winter wheat is affected more than spring wheat because environmental conditions are more conducive. Symptoms appear on stems directly above or below the soil surface. Stems develop a light tan to yellow-brown, eye-shaped lesion that expands upward and around the stem. The lesion typically has a dark colored center and is lighter toward the edges. As disease progresses, lesions penetrate successive leaf sheath layers until it infects the true stem. One or more lesions can occur on a single stem. Lesions may eventually girdle the stem, causing dead standing stems (white heads) and/or lodging. Symptoms can be observed from stem extension stages through ripening.
Cool, wet weather typical of fall and early spring is conducive to disease. A mild winter followed by a cool spring is particularly favorable for the pathogen. Early seeding also favors eyespot.
Eyespot resistant wheat varieties exist. Other management strategies include delayed fall planting (to avoid inoculum) and using a three-year crop rotation. If disease is severe, consider a lower planting density to reduce humidity in the canopy. Reduced tillage can decrease pathogen spread. Fungicide seed treatments may provide limited protection, but pathogen infection can occur after fungicide protection diminishes. Several foliar-applied fungicides are available; these must be applied near but prior to appearance of the first node on the main stem for greatest effectiveness.
Gallery images: M. Burrows.