CORN (ZEA-MAYS) INJURY FOLLOWING USE OF CLOMAZONE, CHLORIMURON, IMAZAQUIN, AND IMAZETHAPYR

This study examined the response of com to clomazone, chlorimuron, imazaquin, and imazethapyr the year following their application to soybeans. Herbicides were surface-applied from one-half to three times the labeled application rates. Soybeans were planted the year of application and crop tolerance was evaluated. Corn was planted in rotation the following season. Soybeans were tolerant of all four herbicides. The highest rates of clomazone, chlorimuron, and imazaquin injured the com early in the season. imazethapyr did not influence com growth. Visual estimates of clonazone injury were as high as 39% chlorosis. Seedling dry weight reductions at the highest chlorimuron and imazaquin rates were 32% and 24%, respectively. Although corn was injured by higher rates of clomazone, imazaquin, and chlorimuron at the 3-leaf stage, none of the herbicides significantly reduced grain yield. This study suggests that these herbicides can carry over and injure com, especially if labeled application rates are exceeded. However, low to moderate early season injury to com may not affect grain yield.