Rapid adoption of glyphosate-resistant (GR) corn hybrids has led to the reemergence of volunteer corn as a problematic weed in soybean and has made controlling the initial stand of corn in a replant situation more difficult. If volunteer corn in soybean or the initial corn stand in a replant situation is not controlled, yield loss can occur. Clethodim and glufosinate are often used to control GR corn in corn replant situations and in soybean. The objectives of this research were to evaluate the response of two hybrid corn varieties and their F₂ progeny to clethodim and glufosinate and to evaluate the effect of plant nitrogen (N) concentration on clethodim and glufosinate efficacy. First, a dose-response study was conducted with clethodim and glufosinate on DeKalb 60-18 and 60-18F₂, and DeKalb 63-42 and 63-42F₂ to compare the response of the hybrids and their F₂ progeny to the herbicides. DeKalb 63-42 was more tolerant to clethodim than 60-18 and 60-18F₂. No differences were found between the hybrids and their respective F₂ progeny in the response to clethodim or glufosinate. In a second dose-response study assessing the effect of N conditions on herbicide efficacy, both clethodim and glufosinate were less injurious to plants growing in low N than in high N availability.

Nomenclature: Clethodim; glufosinate; corn Zea mays L.; soybean Glycine max (L.) Merr.