INFLUENCE OF ADJUVANTS AND DESMEDIPHAM PLUS PHENMEDIPHAM ON VELVETLEAF (ABUTILON-THEOPHRASTI) AND SUGAR-BEET RESPONSE TO TRIFLUSULFURON

Greenhouse studies determined the influence of 14 adjuvants and desmed ipham plus phenmedipham on velvetleaf control and sugarbeet injury by triflusulfuron. A second study determined if six adjuvants, or desmedi pham plus phenmedipham, influenced C-14-triflusulfuron absorption by c otyledon or first true leaves of velvetleaf. Triflusulfuron applied tw ice at 4.4 g ai ha(-1) (split application), alone or in combination wi th any adjuvant, did not reduce sugarbeet dry weight. Desmedipham plus phenmedipham applied twice at 370 g ai ha(-1) (split application) red uced sugarbeet dry weight 3%. The addition of an adjuvant to desmediph am 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)) plu s desmedipham plus phenmedipham compared to desmedipham plus phenmedip ham plus the respective adjuvant alone. Velvetleaf was most easily con trolled in the cotyledon stage of growth. Velvetleaf control by triflu sulfuron increased from 0 (no adjuvant) to 80% by the addition of Scoi l or Sylgard 309 plus UAN. Cotyledonary leaves of velvetleaf absorbed 28% more C-14-triflusulfuron than first true leaves. Adjuvant increase d C-14-triflusulfuron absorption by cotyledonary leaves from 15% (no a djuvant) to 48 to 90%. Desmedipham plus phenmedipham decreased velvetl eaf control by triflusulfuron plus X-77 or X77 plus UAN compared to tr iflusulfuron plus the adjuvant alone. Velvetleaf control by triflusulf uron plus other adjuvants was not reduced by desmedipham plus phenmedi pham. Absorption of C-14-triflusulfuron by cotyledonary and first true leaf velvetleaf decreased when desmedipham plus phenmedipham was adde d to triflusulfuron plus Dash, Dash plus UAN, X-77, X-77 plus UAN, and Sylgard 309 plus UAN.