Selectivity mechanisms of sethoxydim between red fescue (Festuca rubra) and tall fescue (Festuca arundinacea)

The herbicidal action of sethoxydim, 2-[1-(ethoxyimino)-butyl]-5-[2-(ethylthio) propyl)-3-hydroxy-2-cyclohexen-1-one, on red fescue (Festuca rubra L.) and tall fescue (Festuca arundinacea SHREB.) was studied in hydroponic and callus culture. Red fescue as a tolerant plant and tall fescue as a susceptible plant responded quite differently to root treatment with sethoxydim. Uptake, translocation, and metabolism of 14C-sethoxydim root-applied to red fescue and tall fescue were examined to elucidate the selective herbicidal action of sethoxydim between the plants. The amount of absorbed and translocated radioactivity was rather greater in tolerant red fescue than in susceptible tall fescue. The two species yielded similar metabolites and exhibited a similar degradation pattern.Callus culture derived from both fescue species also reacted differently as well as in the hydroponic study.Tolerance to sethoxydim in red fescue appears to be related to some physiological differences at the site of action rather than to differential uptake, translocation, and/or metabolism in whole plants in hydroponic culture, in comparison to tall fescue.