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Title: Vapor movement of the synthetic auxin herbicides, aminocyclopyrachlor and its methyl ester under laboratory and enclosed chamber environments

Author
item STRACHEN, STEPHEN - Dupont Company
item CASINI, MARK - Dupont Company
item HELDRETH, KATHLEEN - Dupont Company
item SCOCAS, JOSEPH - Dupont Company
item NISSEN, SCOTT - Colorado State University
item BUKIN, BEKIR - Colorado State University
item LINDENMAYER, BRAD - Colorado State University
item Shaner, Dale
item WESTRA, PHIL - Colorado State University

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2010
Publication Date: 4/1/2010
Citation: Strachen, S.D., Casini, M.S., Heldreth, K.M., Scocas, J.A., Nissen, S., Bukin, B., Lindenmayer, B., Shaner, D.L., Westra, P. 2010. Vapor movement of the synthetic auxin herbicides, aminocyclopyrachlor and its methyl ester under laboratory and enclosed chamber environments. Weed Science. 58:103-108.

Interpretive Summary: Weed management is critical for control of invasive weeds. Aminocyclopyrachlor is a newly discovered herbicide for the control of many broadleaf invasive weeds. A potential problem with any new herbicide is off site movement due to vaporization of the herbicide. In this study we examined the potential volatility of this new herbicide and its methyl ester. We found that aminocyclopyrachlor is non-volatile, whereas aminocyclopyrachlor methyl ester volatility was similar to responses to dicamba under enclosed incubation conditions but were less than dicamba in outdoor, open-air environments. The results show that aminocyclopyrachlor can be safely used with little risk to non-target plants while more studies are needed to better understand the risk of injury to non-target plants due to vapor movement of aminocyclopyrachlor methyl ester under field applications.

Technical Abstract: Aminocyclopyrachlor (DPX MAT28) a newly discovered synthetic auxin herbicide and its methyl ester (DPX KJM44) appear to control a number of perennial broadleaf weeds. The potential volatility of this new herbicide and its methyl ester were determined under laboratory conditions and were also compared to dicamba and aminopyralid using enclosed chamber and open air plant bioassays. Bioassays consisting of visual estimates of epinastic responses and kidney bean and soybean leaf width measurements were developed to measure vapor release from glass and plastic. Vapor release of aminocyclopyrachlor from glass surfaces was undetectable under laboratory conditions, and no phytotoxic responses were observed when plants were exposed to vapors emanating from various surfaces. Results were similar with aminopyralid indicating the risk of plant injury from vapor movement of aminocyclopyrachlor and aminopyralid was very low. When combined with 1% MSO, vapor release of aminocyclopyrachlor methyl ester reached 86%192 hours after application to glass surfaces. Phytotoxic responses of plants exposed to vapors emanating from various surfaces treated with aminocyclopyrachlor methyl ester were similar to responses to dicamba under enclosed incubation conditions but were less in outdoor, open-air environments. Studies are needed to better understand the risk of injury to non-target plants due to vapor movement of aminocyclopyrachlor methyl ester under field applications.