Cause The fungus, Tilletia indica, which can be introduced in contaminated seed. The fungus may become established as persistent spores in soil. It is not currently known to be in Pacific Northwest soils. If it or the disease were detected in locally produced wheat, the industry could suffer serious economic damage because the fungus is strictly regulated in international and domestic seed and grain trades.
Symptoms Karnal bunt is at best difficult to detect and identify in the field. A microscope and biochemical tests are required to accurately identify the pathogen. The most conspicuous symptom is the presence of small numbers of harvested seeds containing tissue that is gray at first but later turns black. Discoloration often is limited to the embryo end only but may extend over the entire kernel.
Cultural control Controls have not been determined for this region. Pathogen-free seed continues to be the most effective way to prevent introducing the karnal bunt pathogen into Pacific Northwest wheat.