EFFECTS OF TILLAGE, CULTIVAR, AND PLANTING DATE ON PERCENTAGE OF SOYBEAN LEAVES WITH SYMPTOMS OF SUDDEN-DEATH SYNDROME

A 4-year experiment, 1991 to 1994, was conducted in a field where sudd en death syndrome (SDS) had previously been observed. The objective wa s to determine the effects of tillage, planting date, and soybean cult ivar on the percentage of leaves with symptoms of SDS at R6 growth sta ge. The soybean cultivars Essex, Forrest, Hartwig, and Rhodes were eac h planted in 75-cm-wide rows in disk-till, ridge-till, and no-till plo ts. The planting dates were mid-May, mid-June, and late June to early July each year. Symptoms of SDS developed in 1991, 1992, and 1994, but in not 1993. There were significant year x cultivar (P = 0.0001) and tillage x planting date x cultivar (P = 0.05) interactions for the per centage of leaves with symptoms of SDS. Essex, Forrest, and Rhodes had a greater percentage of leaves with symptoms of SDS than did Hartwig in 1991 and 1994; differences among cultivars did not occur in 1992. T he percentage of Essex, Forrest, and Rhodes leaves with symptoms of SD S was greater for no-till than for either disk-till or ridge-till in m id-May plantings. There were no significant correlations between the p ercentage of leaves with SDS and yield.