Effect of Timing and Adjuvants on the Efficacy of Reduced Herbicide Rates for Sweet Corn (Zea mays)

Abstract

The efficacy of reduced rates of metolachlor plus cyanazine for weed control in sweet corn was evaluated over a 2-yr period. Early postemergence (POST) and POST herbicide applications at reduced rates gave control of broadleaf weeds comparable to control at the 1 × rate, except for the early POST application at the ¼ × rate in 1993. Preplant incorporated (PPI) and preemergence (PRE) herbicide applications at reduced rates gave poor broadleaf weed control, except for the PRE application at the ½ × rate in 1993. Early POST applications at the ¼ × rate resulted in significantly reduced grass control in 1994, while POST applications at the ¼ × rate gave significantly reduced grass control both years. Generally, POST applications controlled broadleaf weeds better than early POST applications, while grass control with early POST applications was superior to POST applications at reduced rates. Preemergence and PPI applications at reduced rates gave poor broadleaf weed control but satisfactory grass control. Preplant incorporated applications at reduced rates resulted in reduced yield both years, while PRE applications at reduced rates reduced yield only in 1994. Early POST and POST applications at reduced rates did not affect sweet corn yield. The addition of adjuvants to the ¼ × application rate had no effect on weed control or yield.