Response of Corn to Multiple Defoliation Events.

Current National Crop Insurance Services (NCIS) Corn Loss Instructions provide a procedure for assessing yield losses to a corn fields damaged by more than one hail storm on different dates and stages of development during the growing season. As hybrid genetics improve and plant populations increase over time, it is necessary to assess whether these changes influence corn response to defoliation differently than in the past. A multi-state (IL, MN and OH) study was undertaken to determine how much yield loss occurs in corn subjected to multiple defoliation events and compare these losses with those indicated by current NCIS Corn Loss Instructions. Effects of multiple defoliations on other traits of economic importance including maturity, plant and ear height and stalk lodging, were also considered. Actual yield losses, averaged across leaf removal treatments, were slightly lower than the NCIS chart loss estimates. However, treatments which included a 50% leaf loss at the tassel stage resulted in yield losses that were only about half of the chart loss estimates.