Occurrence of the Bud Blight Disease of Soybeans under Field Conditions

The chief purpose of this investigation is to determine the extent to which varieties of soybeans differ under various field conditions in their degree of infection with bud blight, a disease caused by the tobacco ring-spot virus, Annulus tabaci Holmes. Although this disease has been recognized only in rather recent years, it has come to do considerable damage and materially curtails crop yields in Midwestern producing areas. Disease observations were made in three varietal nurseries grown in cooperation with the regional soybean laboratory. Some varieties and strains were in each test were significantly resistant to bud blight as measured by the amount of natural infection. In most cases plants became infected so late in the season and to such a light degree that seed production was nearly normal. In view of there being no known control for bud blight of soybeans and the fact that the severity of the disease is becoming greater with each passing season, it would seem advisable to investigate further the nature of resistance to this disease and its utilization in varietal improvement. Advisor: T. A. Klesselbach