Note the black sporulation of this fungus in place of seed heads.
Photo by Paul Koepsell, 1983.
Cause Pyrenophora avenae (asexual: Drechslera avenae; syn. sexual: Helminthosporium avenaceum; asexual: D. avenaceum), a fungus that overwinters on old straw or stubble.
Cause Manganese deficiency. The problem is localized mostly in areas in northern and extreme eastern Idaho.
Symptoms Light green to gray-brown spots and streaks develop mainly on leaves. Plants may be greatly reduced in height and yield. The entire plant may be yellow if the condition is severe.
Cultural control Apply 3 lb/A manganese to foliage or 15 to 25 lb/A manganese sulfate to soil.
Cause Ustilago segetum (= U. kolleri), a fungus carried on seed.
Cause Unfavorable growing conditions, especially during heading. Frost, poor soil, and hot winds during flowering are common causes. Severe barley yellow dwarf virus infection also causes blast.
Symptoms Florets turn white, and parts or all of the kernels fail to develop. Panicle tips or bases are most often affected.
Cultural control Plant varieties recommended for the area.
Cause A bacterium, Pseudomonas syringae pv. coronafaciens, carried in seed or overwintered in old oat straw. Moist weather favors the disease. Resistant varieties are available elsewhere, but resistance of varieties common in the Pacific Northwest is unknown.
