QUACKGRASS (ELYTRIGIA REPENS) CONTROL IN CORN (ZEA-MAYS) WITH NICOSULFURON AND PRIMISULFURON

Quackgrass is a serious weed problem in the northern United States and southern Canada. Field experiments were conducted in 1990 and 1991 to examine the effect of herbicide rate, application timing, quackgrass growth stage, and cultivation on quackgrass control with nicosulfuron and primisulfuron in corn. Nicosulfuron (35 g ai/ha) and primisulfuron (40 g ai/ha) each provided 84% or greater control of two-leaf plants and 93% or greater control of four-leaf quackgrass plants. Sequential applications of both nicosulfuron and primisulfuron provided greater s eason-long control than single applications of the same rate on two-le af but not four-leaf quackgrass. Cultivation 10 d after nicosulfuron o r primisulfuron application often increased early-season control, but by corn harvest few differences were observed. Postemergence (POST) ap plications of nicosulfuron and primisulfuron provided at least 88% con trol, compared with 66 to 86% from an early preplant application of gl yphosate. Corn yields were similar regardless of the quackgrass contro l program.