Weed control in glyphosate-resistant sugarbeet (Beta vulgaris L.)

Abstract

A two-year study examined weed control in glyphosate­ resistant sugarbeet with various glyphosate rates and application timings, and glyphosate in combination with residual herbicides or ammonium sulfate (AMS). Treatments that included two or three applications of glyphosate regardless of rate or glyphosate applied once in combination with dimethenamid-p resulted in redroot pigweed, common lambsquarters and hairy nightshade control equal to, or greater than, a standard herbicide program. T he addition of AMS to glyphosate did not affect weed control efficacy. A single application of glyphosate did not provide season long weed control in 1998, but was effective in controlling all weeds but redroot pigweed in 1999. Generally, sugarbeet root yield was similar in plots treated with glyphosate or standard herbicide programs. Additional Key Words: Desmedipham, ethofumesate, phenmedipham, dimethenamid-p, sethoxydim, triflusulfuron, redroot pigweed, common lambsquarters, bamyardgrass, hairy nightshade. Weed control in sugarbeet (Beta vulgaris L.) is difficult and expensive requiring repeated applications offour to five herbicides during the growing season to control weeds in current production systems. Sugarbeet is sensitive to many herbicides, so herbicides that control a wide range of weeds often are not registered for sugarbeet production. Lower cost herbicides that control a wider range ofweeds would benefit sugarbeet producers. Glyphosate is a non-selective, postemergence, systemic herbicide that has activity on a wide range ofbroadleafand grass species