Powdery Mildew Symptoms on Wheat

Powdery Mildew (fungus - Erysiphe graminis f. sp. tritici): Powdery mildew is usuall found only on the leaves, but the fungus may attack all aboveground parts of the plant. It is noticeable first as small, irregular or circular, light gray spots on the upper surface of a leaf. The spots enlarge as the fungus grows and often may involve large parts of the leaf. As the spots age, the fungus on them takes on a flowery appearance which is due to the production of an enormous number of spores. Often the lower surface of the leaf beneath the diseased spots turns yellow and older parts of the spots turn brown. Affected leaves become deformed and crinkled and in severe cases they become brittle or they may die prematurely. As affected wheat approaches maturity, small, black fruiting structures (seen as black specks) may be scattered throughout the fungus growth on infected spots. This disease is not seed-borne but can be soil-borne. Close grazing to keep top growth reduced to a minimum will allow sunlight and air to keep the crown of the plant dried out, thus reducing the occurrence of powdery mildew. Rotations with non-host plants will also help reduce the soil-borne phase of this disease. Chemical control may be economical on high yield potential wheat.