Effect of Three Tillage Practices on Development of Northern Corn Leaf Blight (Exserohilum turcicum) Under Continuous Corn. W. L. Pedersen, Associate Professor, Departments of Plant Pathology and Agronomy, University of Illinois, Urbana 61801. M. G. Oldham, Agronomist, Department of Agronomy, University of Illinois, Urbana 61801. Plant Dis. 76:1161-1164. Accepted for publication 1 August 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-1161.

Corn hybrid A632 × 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 × A619, B73 × Mo17, and B73 × LH38, were planted in the same field in 1986. The experiment was repeated by planting and inoculating A632 × 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 × 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 × A619. The more resistant hybrids, B73 × Mo17 and B73 × LH38, had significant negative correlations between lodging and yield for all tillage practices.