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Title: WEED RESEARCH IN MINT

Author
item Boydston, Rick
item BAKER, RAY - WSU, PROSSER, WA
item Birch, Lyle

Submitted to: Proceedings Tri State Mint Convention
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2001
Publication Date: 1/1/2002
Citation: BOYDSTON, R.A., BAKER, R., BIRCH, L.M. WEED RESEARCH IN MINT. PROCEEDINGS OF THE 2ND ANNUAL TRI STATE MINT CONVENTION, BOISE, ID, P. 16-37. JAN 2002.

Interpretive Summary: Weeds lower mint oil yield and quality. Weed control represents a major production cost and investment of time for growers. The goal of this research is to develop improved weed control methods in spearmint and peppermint and to identify promising new herbicides on spearmint and peppermint. Several herbicides were identified that were safe on mint while controlling several problem weeds. Flumioxazin, sulfentrazone, fluroxypyr, and a new formulation of pendimethalin controlled weeds in mint and offer several new herbicide chemistries for use in mint. Residue data needed for registration of flumioxazin in spearmint and peppermint were completed and submitted to IR-4 headquarters. Western salisfy, a commonly missed weed in mint fields was controlled with oxyfluorfen, terbacil, flumioxazin and sulfentrazone in greenhouse tests.

Technical Abstract: Salsify was controlled in greenhouse trials with preemergence applied flumioxazin, sulfentrazone, terbacil and oxyfluorfen. Sulfentrazone and flumioxazin applied preemergence in fall or spring were safe on native spearmint and peppermint, whereas halosulfuron and pyrithiobac were not. Sulfentrazone suppressed yellow nutsedge. Flumioxazin and sulfentrazone controlled kochia and common lambsquarters well. Fluroxypyr, pyrithiobac, and 2,4-DB applied postemergence suppressed field bindweed growth, but did not reduce the number of field bindweed in native spearmint. Native spearmint was injured to varying degrees by fluroxypyr applied at four rates and three timings. Initial injury to established peppermint was less with a 3.8 lb ai/gal formulation of pendimethalin than with the standard 3.3 lb ai/gal formulation. Sulfentrazone, two formulations of pendimethalin, and terbacil controlled annual weeds well with minimal injury to newly planted peppermint. Flumioxazin applied preemergence at 0.047 and 0.094 lb ai/a slightly injured newly planted peppermint and controlled annual weeds well.