See:
Wheat (Triticum aestivum) - Bacterial Streak and Black Chaff (Bacterial Streak)
Cause Often the cause is unknown, but it may be a deficiency or imbalance in mineral nutrition (especially minor elements such as chloride, manganese, or zinc), an inherited genetic dysfunction in wheat, or a combination of these and other abiotic and biotic agents. In low rainfall regions of the Pacific Northwest, the disease is usually associated with a deficiency in chloride nutrition. Fungicides and stubble burning are not effective controls, and little is known about the effects of tillage and crop rotations.
Symptoms Symptoms first appear in March. Spots' characteristics may differ depending on the lesion's age, wheat variety, weather, and other factors. Typically, the first symptom is a tiny brown spot or fleck on lower leaves. A yellowish halo may or may not surround the spot. Spots enlarge into brown, necrotic areas, oval or irregularly shaped, with or without yellowish halos. Sometimes the symptom is simply a yellowish, rather than brown, spot of variable size and shape. The disease often becomes more severe on lower leaves as it establishes on younger leaves. If severe, older leaves die prematurely, and up to 60% of the flag leaf may turn brown and die. Yield can be reduced 20% or more. Symptoms easily are confused with those of Septoria blotch, tan spot, bacterial leaf blight, and certain minor-element deficiencies.
Cultural control
- Application of a chloride-containing fertilizer reduces the occurrence and severity of this disease in many areas. Chloride may be applied to soil before planting or sprayed onto foliage during seedling growth, before leaf spot symptoms become evident.
- Plant the least susceptible varieties. The varieties Dusty, Tres, Hyak, Hill 81, Moro, and Buchanan are moderately resistant. The varieties Lewjain, Yamhill, Cashup, Andrews, Oveson, Wanser, Basin, Daws, and Eltan are moderately susceptible. The varieties Malcolm, Kmor, Batum, Madsen, and Stephens are very susceptible.