EFFECT OF 3 TILLAGE PRACTICES ON DEVELOPMENT OF NORTHERN CORN LEAF-BLIGHT (EXSEROHILUM-TURCICUM) UNDER CONTINUOUS CORN

Corn hybrid A632 X A619 was planted in 1985 on 0.6 ha, and plants were inoculated 6 wk later with Exserohilum turcicum race 2. A severe epidemic of northern corn leaf blight developed. Three tillage treatments, ridge-till, mulch-till, and no-till, were established. and three corn hybrids, A632 X A619, B73 X Mo17, and B73 X LH38, were planted in the same field in 1986. The experiment was repeated by planting and inoculating A632 X A619 on 0.6 ha in 1986 and reevaluating the three tillage treatments and three corn hybrids in 1987. Northern corn leaf blight was more severe under no-till than mulch-till for the susceptible hybrid A632 X A619 in both years. Disease severity levels for ridge-till were similar to those for no-till in 1986 but were similar to those for mulch-till in 1987. Highest yields were obtained from ridge-till and mulch-till plots for both years, whereas no-till plot yields were consistently the lowest. A significant negative correlation occurred between area under disease progress curve (AUDPC) and yield and a significant positive correlation between AUDPC and lodging for A632 X A619. The more resistant hybrids, B73 X Mo17 and B73 X LH38, had significant negative correlations between lodging and yield for all tillage practices.