Barnyardgrass (Echinochloa crus-galli var. crus-galli) is the most difficult-to-control weed that infests rice fields in Korea. The objectives of this research were to confirm ALS (acetolactate synthase)- and ACCase (Acetyl-CoA carboxylase)-inhibiting herbicide-resistant barnyardgrass in Korea and to determine sensitivity and efficacy of rice herbicides applied for control of resistant and susceptible barnyardgrass biotypes. The putative seeds of ALS- and ACCase-resistant barnyardgrass biotype were collected from rice fields in fall 2010. The responses of barnyardgrass biotypes to 10 rates (0 to 10X) of ACCase inhibitors, cyhalofop-butyl and metamifop, and ALS inhibitors, priminobac-methyl, penoxsulam and flucetosulfuron, were evaluated in a dose�response bioassay in a greenhouse. On the basis of the values at GR50 (concentration of respective herbicides required for 50% inhibition of dry weight), the analysis showed about 19 to 42-fold resistance depending upon the type of ALS- and ACCase-inhibiting herbicides being investigated and susceptible biotype used for comparison. The resistant biotype had a reduced sensitivity to ALS- and ACCase-inhibiting herbicides. These results suggested a cross-resistance between ALS- and ACCase-inhibiting herbicides that resulted in effectiveness for control of barnyardgrass. Barnyardgrass biotypes were effectively controlled (=?90%) with mefenacet, and fentrazamide by the two-leaf stage, whereas oxadiazon, thiobencarb and butachlor provided over 90% control by the one-leaf stage of the resistant biotype.

Control and cross-resistance of barnyardgrass to ALS- and ACCase-inhibitors in rice field in Korea

248th National Meeting (2014)

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