Relationships Between Yield of Three Maize Hybrids and Severity of Southern Leaf Blight Caused by Race O of Bipolaris maydis

Severity of SLB in mid- to late August ranged from 0-5% on FR27×Pa91 at Tolono, IL, to 10-40% on Pioneer 3183 at Urbana, IL. Regressions of yield on area under the curve and on severity of SLB were significant for seven, six, and four of the nine locations for Pioneer 3183, B73×Mo17, and FR27×Pa91, respectively. Yield of FR27×Pa91 and B73×Mo17 was reduced about 0.7-0.8% for each 1% increase in severity of SLB between 0 and 25%. For Pioneer 3183, yield was reduced about 0.6-0.7% for each 1% increase in severity between 0 and 25%