This is the reason for the name partial bunt. Other smut fungi causing loose smut and stinking smut invade the embryo or germinating seedling and subsequently destroy the entire seed head. Also, other smut fungi destroy all heads on a plant. Because of this, the disease is difficult to detect in the field. The fungus may be present for several years and build up slowly before it is recognized.
Teliospores are airborne andeasily disseminated during the harvesting process.
Seed and soil in an entire field can be contaminated from a few bunted kernels during the harvesting process. Teliospores may be disseminated hundreds of miles or more by wind, but no precise information about long-distance dissemination is available. Karnal bunt seldom causes significant economic losses to wheat in the field. The fungus does not produce any toxic Figure 2. Disease cycle of Karnal bunt caused by Tilletia indica.