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.