Yellow nutsedge (Cyperus esculentus L.) control in corn with various rates of halosulfuron

There are a limited number of herbicide options that provide commercially acceptable control of yellow nutsedge in corn. A study consisting of nine field experiments was conducted during 2013-2016 in growers' fields in Ontario to evaluate the efficacy of glyphosate plus various rates of halosulfuron applied after emergence (post-emergence, POST) for the control of yellow nutsedge in glyphosate-resistant corn. Glyphosate (900 g a.e. ha(-1)) plus halosulfuron applied POST at the registered rate of 34-68 g a.i. ha(-1) caused minimal injury in glyphosate-resistant corn. The predicted halosulfuron rates needed to control yellow nutsedge 50%, 80%, and 90% were 3, 24, and >140 g a.i. ha(-1) at 4 weeks after herbicide application (WAA) and 2, 13, and 73 g a.i. ha(-1) at 8 WAA, respectively. The predicted halosulfuron rates required to reduce yellow nutsedge density 50%, 80%, and 90% were 13, 42, and 109 ga.i. ha(-1), respectively. In addition, the predicted halosulfuron rates required to reduce yellow nutsedge dry weight 50%, 80%, and 90% were 6, 23, and 54 g a.i. ha(-1), respectively. Contrasts comparing halosulfuron (35 g a.i. ha(-1)) with other herbicides showed that glyphosate plus halosulfuron provided as much as 35% greater control of yellow nutsedge than glyphosate plus bentazon (1080 g a.i. ha(-1)) and as much as 22% greater control of yellow nutsedge than glyphosate plus tembotrione/thiencarbazone (45 g a.i. ha(-1)).