Interaction between diclofop‐methyl and 2,4‐D in wild oat (Avena fatua L.) and cultivated oat (Avena sativa L.), and fate of diclofop‐methyl in cultivated oat

Summary Influence of 2,4‐D on toxicity of diclofop‐methyl to Avena sativa (cv. Selma) and Arena fatua at 2·5 leaf stage has been evaluated under controlled conditions. Effects of 2,4‐D on the fate of diclofop‐methyl in cultivated oat have also been studied. Mixture with 2,4‐D reduced the toxicity of diclofop‐methyl to both species. When applied immediately after diclofop‐methyl treatment, 2,4‐D still reduced herbicide toxicity to wild oat. This reduction was smaller in cultivated oat. and was only observed at higher phytotoxicity. No interaction was observed when a 10‐day period separated the two applications. In mixture, 2,4‐D enhanced diclofop‐methyl penetration and diclofop acid conjugation in cultivated oat, and it slightly increased conjugation when applied separately. None of these effects clearly explain the reduction of diclofop‐methyl toxicity by 2, 4‐D in cultivated oat. Other processes are possibly involved and could be connected with the site of action of diclofop‐methyl.