Effect of Herbicide Rotations on Enhanced Herbicide Biodegradation and Wild-Proso Millet (Panicum miliaceum) Control

Abstract

A 6-yr field study was conducted to determine the effect of herbicide rotations on enhanced biodegradation of EPTC applied with and without dietholate, and on long-term control of wild-proso millet in sweet corn. Alachlor plus pendimethalin plus cyanazine or cycloate plus cyanazine for 1 yr following previous EPTC plus cyanazine applications reduced enhanced EPTC biodegradation in 3 of 4 and 2 of 3 yr, respectively. Enhanced biodegradation of EPTC applied with dietholate was reduced in 1 of 2 yr when EPTC plus dietholate plus cyanazine treatments were followed for 1 yr by alachlor plus cyanazine, pendimethalin plus cyanazine, or cycloate plus cyanazine, but was not reduced in 2 of 3 yr when EPTC plus dietholate plus cyanazine treatments were followed for 1 yr by alachlor plus pendimethalin plus cyanazine. Dietholate biodegradation was enhanced in soils treated 1, 2, or 3 yr previously with one application of EPTC plus dietholate plus cyanazine. After 3 yr of repeated use, cycloate biodegradation was also enhanced. Continuous use of EPTC plus cyanazine and EPTC plus dietholate plus cyanazine over 6 yr provided an average of only 46 and 64% wild-proso millet control, respectively. When applied once every second, third, or fourth year in rotation with alachlor plus pendimethalin plus cyanazine or cycloate plus cyanazine, EPTC plus cyanazine provided 83, 86, and 95% wild-proso millet control, respectively. EPTC plus dietholate plus cyanazine applied every second, third, or fourth year in rotation with cycloate plus cyanazine, alachlor plus cyanazine, pendimethalin plus cyanazine, or alachlor plus by pendimethalin plus cyanazine provided 88, 91, and 95% wild-proso millet control, respectively.