Influence of Adjuvants and Desmedipham plus Phenmedipham on Velvetleaf (Abutilon theophrasti) and Sugarbeet Response to Triflusulfuron

Abstract

Greenhouse studies determined the influence of 14 adjuvants and desmedipham plus phenmedipham on velvetleaf control and sugarbeet injury by triflusulfuron. A second study determined if six adjuvants, or desmedipham plus phenmedipham, influenced14C-triflusulfuron absorption by cotyledon or first true leaves of velvetleaf. Triflusulfuron applied twice at 4.4 g ai ha−1(split application), alone or in combination with any adjuvant, did not reduce sugarbeet dry weight. Desmedipham plus phenmedipham applied twice at 370 g ai ha−1(split application) reduced sugarbeet dry weight 3%. The addition of an adjuvant to desmedipham plus phenmedipham reduced sugarbeet dry weight 21 to 66% depending on the adjuvant. Sugarbeet injury was not greater when triflusulfuron was applied with any adjuvant (except urea ammonium nitrate (UAN)) plus desmedipham plus phenmedipham compared to desmedipham plus phenmedipham plus the respective adjuvant alone. Velvetleaf was most easily controlled in the cotyledon stage of growth. Velvetleaf control by triflusulfuron increased from 0 (no adjuvant) to 80% by the addition of Scoil or Sylgard 309 plus UAN. Cotyledonary leaves of velvetleaf absorbed 28% more14C-triflusulfuron than first true leaves. Adjuvant increased14C-triflusulfuron absorption by cotyledonary leaves from 15% (no adjuvant) to 48 to 90%. Desmedipham plus phenmedipham decreased velvetleaf control by triflusulfuron plus X-77 or X77 plus UAN compared to triflusulfuron plus the adjuvant alone. Velvetleaf control by triflusulfuron plus other adjuvants was not reduced by desmedipham plus phenmedipham. Absorption of14C-triflusulfuron by cotyledonary and first true leaf velvetleaf decreased when desmedipham plus phenmedipham was added to triflusulfuron plus Dash, Dash plus UAN, X-77, X-77 plus UAN, and Sylgard 309 plus UAN.