OCCURRENCE OF SOYBEAN SUDDEN-DEATH SYNDROME IN EAST-CENTRAL ILLINOIS AND ASSOCIATED YIELD LOSSES

Sudden death syndrome (SDS) of soybeans, causal organism Fusarium solani, occurred for the first time in epidemic proportions in east-central Illinois in 1993. SDS occurred in 46% of the soybean fields, based on air and ground surveys. Within fields containing plants with SDS, the percent area affected ranged from 1 to 70% with an average of 7.3 and 13.9% for ground and aerial surveys, respectively. Soil samples taken in 25 fields in areas where all plants showed SDS symptoms and in adjacent areas where plants appeared healthy did not differ in cyst populations of soybean cyst nematode (Heterodera glycines). Disease severity and yield components were compared from replicated plots at an experimental farm and in a commercial field and in a nonreplicated commercial field. Diseased plants from infested areas had fewer pods and seeds and less 300-seed weights. Plant yields were 46, 41, and 20% less for plants in plots with a high incidence of SDS than were the yields for those with a low incidence of SDS in a nonreplicated commercial field, replicated plots at an experimental farm, and a commercial field, respectively. Seed germination was less and the frequency of Phomopsis spp. was greater on seeds harvested from plants in plots with a high occurrence of SDS compared to plots with a low occurrence of SDS.