Outbreak of Ergot (Claviceps purpurea) in Iowa Barley, 1996

An outbreak of ergot, caused by Claviceps purpurea, occurred in barley (Hordeum vulgare) grown in northeastern Iowa and southwestern Wisconsin in 1996. In a nine-county area of intensive dairy production in Iowa, approximately 40% of the barley hectarage (approximately 1,200 ha) was affected by the disease. Several cultivars were affected, including Robust, Excel, and Chilton, and no differences in ergot contamination levels were observed among cultivars. Barley samples examined by the Iowa State University Seed Science Center averaged 0.2% ergot by weight, with a maximum of 0.53%. Prolonged cool, wet weather during heading and greater barley planting than usual contributed to the high incidence of infection, but other influential factors have not been identified. Symptoms were not noticed in barley in the field and much of the infested grain was fed to cattle (primarily dairy cows), resulting in a considerable incidence of ergotism. An estimated 1,000 animals displayed symptoms of ergotism, manifested as loss of milk production and hyperthermia. Approximately 10 to 15 animals died or were destroyed. Ergot also was prevalent in forage grasses, including brome (Bromus spp.), Kentucky bluegrass (Poa pratensis), orchardgrass (Dactylis glomerata), quackgrass (Agropyron repens), and timothy (Phleum pratense). Minor symptoms of ergotism were associated with consumption of infested hay and pasture grasses. Negligible incidences of ergot occur annually in small grains and forage grasses in Iowa; ergotism of this extent has not been observed for several decades. Crop rotation and early harvest of grass hay have been recommended for 1997 to prevent a recurrence of the disease.