Late-Season Weed Control in Glyphosate-Resistant Sugarbeet

Abstract

Field trials were conducted from 2006 through 2008 to determine the influence of ethofumesate applied at planting followed by dimethenamid-p ors-metolachlor applied to emerged sugarbeet for late-season weed control in glyphosate-resistant sugarbeet. The entire plot area was kept weed-free until mid-June by applying glyphosate at the four- and eight-true-leaf sugarbeet growth stages. Glyphosate was not applied from mid-June until late-July to allow weed growth as a measure of the residual benefit from ethofumesate, dimethenamid-p, ands-metolachlor applied earlier in the growing season. Dimethenamid-p was not as effective ass-metolachlor in reducing weed density in mid-July. Late-season weed suppression from boths-metolachlor and dimethenamid-p benefitted from ethofumesate applied at planting. Dimethenamid-p applied when sugarbeet reached the six-true-leaf growth stage reduced weed density and sugarbeet injury more than earlier applications. The lowest weed density in mid-July was achieved whens-metolachlor was applied at the six- to eight-true-leaf sugarbeet growth stage compared to earlier growth stages. A planting time application of ethofumesate followed by two glyphosate applications pluss-metolachlor at the eight-true-leaf sugarbeet growth stage provided 89% more weed control in mid-July than glyphosate alone. Suppressing late-season weed development increased sugarbeet root yield 15% compared with areas not receiving ethofumesate ands-metolachlor.