Susceptibility of crabgrass biotypes (Digitaria ciliaris) to ACCase inhibitor herbicides

Abstract

Species belonging to Digitaria genus are including among major weeds infesting rice and soybeans crops. The objective of this study was to evaluate the differential susceptibility of crabgrass biotypes crops at Rio Grande do Sul State, to clethodim or cyhalofop herbicides. Three experiments were conducted in greenhouse conditions, in the period of 2009-2011 agricultural years. Seeds of Digitaria spp. were collected from different places in the State, covering areas of irrigated rice production and soybeans crops, totalizing 169 biotypes. To evaluate the biotypes sensitivity to the herbicides was applied 225 g a.i. ha^-1 of cyhalofop or 96 g a.i. ha^-1 of clethodim, being selected eight Digitaria ciliaris biotypes with higher and lower tolerances after herbicides application to the studies of response curve doses. It was found four biotypes with higher tolerance to cyhalofop coming from Santa Vitória do Palmar, Viamão, Santa Barbara do Sul and Cruz Alta County, with controls between 50 and 60%. Biotypes of crabgrass were susceptible to clethodim herbicide, with a control superior greater than 90%. The D. ciliaris populations collected in rice and soybeans crops in RS were susceptible to clethodim herbicide when the application was made at recommended dose, while specie susceptibility cyhalofop herbicide was differential among biotypes.