The Georgia Agricultural Experiment Station
College of Agricultural and Environmental Sciences
The University of Georgia
Research Report Number 666
August 2000
Small Grains Updates
Barry M. Cunfer, Department of Plant Pathology, Griffin Campus, Griffin, GA 30223
The dry spring was not conducive for development of foliar diseases. The low level of disease contributed to high yields and grain test weights across the state. However, some losses were encountered on cultivars susceptible to leaf rust. Stagonospora leaf and glume blotch were very low. Symptoms were mostly confined to the lower leaves and very little glume blotch occurred. The most serious disease occurrence was on one farm where over 200 acres were lost because of common bunt or stinking smut. This disease produces a foul odor like dead fish. Spores of the fungus carried on seed invade the seedling when the seed germinates. No damage is seen until heads emerge when the seeds are entirely replaced by smut spores. The smut spores are released during threshing and adhere to the healthy seed. Because so many spores are produced, an infection level near 1 percent one season can result in 50 percent or greater loss the next season. Therefore, the disease may go unnoticed the year before serious loss occurs. Loose smut on oats has a similar life cycle. Loose smut of wheat and barley has a somewhat different life cycle but it is also transmitted only by seed. Smut diseases are very easily controlled by systemic seed treatments. Tebuconazole (Raxil) and difenoconazole (Dividend) are most effective but carboxin (Vitavax) will also give effective control in most cases. Seed protectant fungicides such as captan and thiram will not control smut diseases. Certified seed is inspected for smut diseases and only a very low level is tolerated. Therefore, planting Certified seed is an effective way to control smuts.
Barley yellow dwarf was variable and caused mostly light damage. Take-all root rot caused significant losses in fields with three years of consecutive wheat-soybean doublecropping. Rotation with fallow, oats or canola in place of wheat controls take-all. Wheat should not be grown more than two consecutive years in the same field. Stripe rust was found at very low levels at two locations in the state. The disease was found in several locations in the eastern United States for the first time. The cool spring was favorable for the disease which caused losses in the Mississippi Valley. Stripe rust is unlikely to become a problem in the Southeast.