Control of Acetolactate Synthase–Resistant Shattercane (Sorghum Bicolor) in Field Corn with Kih-485

Abstract

Experiments were conducted in 2004 and 2005 in Virginia to evaluate KIH-485 for shattercane control. KIH-485 was applied to glyphosate-resistant corn at three rates (166, 209, and 250 g ai/ha) and two timings (preemergence [PRE] and postemergence [POST]) and compared to standard rates of S-metolachlor, acetochlor, and pendimethalin. PRE treatments were applied alone, while POST treatments were combined with 1,121 g ai/ha of glyphosate. A single POST application of glyphosate, a nontreated weedy control (WC), and a weed-free control (WFC) were also evaluated. In 2004, at 1 mo after planting (MAP), shattercane was controlled 73, 86, and 93% with the three PRE treatments of KIH-485 compared to only 50, 49, and 48% control with S-metolachlor, acetochlor, and pendimethalin, respectively. Similar levels of shattercane control were also observed with these treatments at 1 MAP in 2005. In both years at 4 MAP, KIH-485 combined with glyphosate applied POST controlled shattercane 96% or greater. However, when glyphosate was combined with S-metolachlor, acetochlor, or pendimethalin, shattercane control was less than 88% in either year. Corn yields with POST applications of KIH-485 plus glyphosate were equivalent to yield from the WFC and greater than yield from any PRE treatment. Early-season shattercane control was promising with KIH-485; however, season-long control only occurred when KIH-485 was applied POST in combination with glyphosate.Nomenclature: Acetochlor, glyphosate, KIH-485, 3-[(5-difluoromethoxy-1-methyl-3-trifluoromethylpyrazol-4-yl)methylsufonyl]-4,5-dihydro-5,5-dimethylisoxazole, S-metolachlor, pendimethalin, shattercane, Sorghum bicolor (L.) Moench SORVU, corn, Zea mays L. ZEAMX