Tolerance of large crabgrass of different ages and strains to propanil.

Abstract

Tolerance of large crabgrass of different ages and strains to propanil was surveyed, and the absorption of propanil by shoots and its hydrolyzing enzyme activity have also been studied.There were no great differences in susceptibility to the herbicide among large crabgrass plants from different locations in Japan at the 4th leaf stage. Significant difference in tolerance was found among large crabgrass plants at different ages, as well as barnyardgrass. The younger large crabgrass and barnyardgrass were more susceptible to propanil and tolerance to the herbicide incre ased as the leaf stage increased. Neither species of plant hydrolyzed the substance even at the 6th leaf stage. The concentration of 14C-radioactivity in large crabgrass at the 3rd leaf stage was much higher than at the 6th.Large crabgrass was shown tolerant to propanil only at the 6th stage, and differential tolerance to the compound in different strains was not found significant. It was suggested that the mechanism of tolerance of large crabgrass at the 6th leaf stage to propanil was not due to the detoxifying hydrolytic activity of the herbicide, but due primarily to the lower absorption of the compound by the shoots.