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Title: SPRAY CARRIER PH EFFECT ON ABSORPTION AND TRANSLOCATION OF TRIFLOXYSULFURON IN PALMER AMARANTH (AMARANTHUS PALMER) AND TEXASWEED (CAPERONIA PALUSTRIS)

Author
item MATOCHA, M - TEXAS COOPERATIVE EXT
item Krutz, Larry
item SENSEMAN, S - TEXAS A&M UNIVERSITY
item Koger Iii, Clifford
item Reddy, Krishna
item PALMER, E - SYNGENTA CROP PRODUCTION

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2006
Publication Date: 12/12/2006
Citation: Matocha, M.A., Krutz, L.J., Senseman, S.A., Koger III, C.H., Reddy, K.N., Palmer, E.W. 2006. Spray carrier ph effect on absorption and translocation of trifloxysulfuron in palmer amaranth (amaranthus palmer) and texasweed (caperonia palustris). Weed Science 54:969-973.

Interpretive Summary: Trifloxysulfuron is a new herbicide labeled for use in cotton. Its chemical properties are affected by pH. Thus, the pH of the spray solution may affect weed control with this compound. The uptake and movement of trifloxysulfuron by two weed species, Palmer amaranth and Texasweed, was evaluated as a function of the spray solution pH: acidic, neutral, and alkaline conditions. Uptake of trifloxysulfuron was greater for Palmer amaranth (88%) compared to Texasweed (29%). Uptake of trifloxysulfuron decreased as the spray solution became more acidic. Adjuvants that increase the spray solution pH may increase the effectiveness of this herbicide.

Technical Abstract: Absorption and translocation of trifloxysulfuron in weed species may be affected by pH of the spray carrier. The objective of this study was to evaluate the absorption and translocation of foliar-applied 14C-trifloxysulfuron in Palmer amaranth and Texasweed at pH 5, 7, and 9 over a period of 4 to 72 h after treatment (HAT). For absorption, effects of time, species, and pH were significant. Absorption averaged over species and pH increased logarithmically from 4 to 72 HAT. Absorption was greater for Palmer amaranth (88%) than for Texasweed (29%) when averaged over time and pH. Absorption averaged over species and time increased in the order of pH 5 (52%) < pH 9 (60%) = pH 7 (61%). The main effects and interaction among harvest interval, species, and pH were significant for the translocation of 14C-trifloxysulfuron. At 24 HAT, translocation was greater in Palmer amaranth compared to Texasweed at all pH levels and harvest intervals. Altering pH did not affect the translocation of trifloxysulfuron in Palmer amaranth. In contrast, translocation of 14C-trifloxysulfuron in Texasweed at 72 HAT increased in the order of pH 5 (5%) < pH 7 (10%) = pH 9 (10%). These data indicate that absorption and translocation of trifloxysulfuron in some weed species may be enhanced by increasing the pH of the spray solution by two pH units above the pKa.