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item RANSOM, C
item Boydston, Rick

Submitted to: Western Society of Weed Science Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2003
Publication Date: 9/7/2004
Citation: Hutchinson, P.S., Ransom, C.V., Boydston, R.A., Beutler, B.R. 2004. Dimethenamid-p: Efficacy and potato variety tolerance. Western Society of Weed Science Meeting Proceedings. 57:56.

Interpretive Summary:

Technical Abstract: Dimethenamid-p is a new preemergence herbicide being developed for use in potato. Trials were conducted in Idaho, Oregon, and Washington in 2001, 2002, and 2003 to determine the efficacy of dimethenamid-p alone at 0.64 lb ai/A, and in tank mixtures with EPTC, metribuzin, pendimethalin, or rimsulfuron. The tank-mix herbicides were also applied alone. In Idaho, late-season control of hairy nightshade, common lambsquarters, and volunteer oat was improved with dimethenamid-p tank mixtures compared with control by dimethenamid-p or the tank mix herbicides alone. Redroot pigweed control with dimethenamid-p + EPTC or pendimethalin was greater than control with those three herbicides applied alone. Kochia control was improved with dimethenamid-p tank mixtures compared with all herbicides applied alone except metribuzin. Hairy nightshade control in Oregon trials was similar to control in Idaho trials. In Washington, dimethenamid-p alone generally controlled hairy nightshade as well as dimethenamid-p tank mixtures, and tank mixtures provided greater control than the tank mix herbicides applied alone. Treatments providing less weed control in these efficacy trials had lower U.S. No. 1 and total tuber yields than the weed-free controls and the tank-mixture treatments. Dimethenamid-p at 0.64 or 1.28 lb ai/A was applied preemergence to six potato varieties, Russet Burbank, Ranger Russet, Russet Norkotah, Shepody, Alturas, and Bannock Russet, in weed-free trials conducted in Idaho in 2002 and 2003 to determine tolerance. There was a significant year by herbicide rate by variety interaction. In 2002, early-season crop injury was <5% and not significant regardless of variety or dimethenamid-p rate. In 2003, the dimethenamid-p rate by variety interaction was significant. Dimethenamid-p at 0.64 and 1.28 lb ai/A resulted in 8 and 13% injury, respectively, to Alturas 2 weeks after treatment (WAT). Injury consisted mainly of stunting. The other varieties had no visible injury 2 WAT. By row closure approximately 6 WAT, little or no injury was evident on any variety. Early injury did not translate to tuber yield reductions. In 2002 and 2003, U.S. No. 1 and total tuber yields of each herbicide-treated variety were not less than tuber yields of the respective untreated variety controls.