Weed control in glufosinate-resistant corn (Zea mays)

The development of glufosinate-resistant corn represents a new weed managem ent system for corn growers. Field experiments were conducted from 1995 to 1997 at four locations in southwestern Ontario. The objective of this study was to determine the effect of timing of weed control relative to the grow th stage of corn with glufosinate applied alone or in combination with resi dual herbicides. Control of all species tested improved with the addition o f atrazine plus dicamba to glufosinate, applied from the two- to eight-leaf stage of corn growth. Based on a 90% weed dry matter reduction, glufosinat e with atrazine plus dicamba controlled common ragweed, common lambsquarter s, and pigweed species at the three-leaf stage of corn and yellow foxtail, barnyardgrass, and large crabgrass at the two-, four-, and eight-leaf stage of corn, respectively. Weed control with glufosinate alone was improved wh en applied at the later growth stages of corn. Glufosinate applied alone at the four-leaf stage of corn controlled common ragweed and common lambsquar ters, whereas pigweed species were controlled effectively at the eight-leaf stage of corn growth. Corn grain yield was consistently higher when glufos inate was applied in combination with residual herbicides, compared to gluf osinate alone. Glufosinate in combination with residual herbicides applied to corn at the three- to five-leaf stage may represent the best timing for weed control. Our data suggested that a tank mixture of glufosinate with ot her postemergence residual herbicides or a split application of glufosinate in combination with cultivation may be required for weed control in glufos inate-resistant corn.