Interaction between imazamethabenz and fenoxaprop in wild oat control and crop tolerance

Abstract

Greenhouse experiments investigated wild oat (Avena fatua L.) control, and crop tolerance of spring and winter wheat (Triticum aestivum L.), and durum wheat (T. turgidum L.) to applications of imazamethabenz and fenoxaprop. Both regression technique and Colby's analysis showed the interaction between imazamethabenz, either liquid concentrate (LC) or suspension concentrate (SC) formulation, and fenoxaprop to be antagonistic. The antagonism was stronger with imazamethabenz-LC than with imazamethabenz-SC. The effect was greater with higher rates of fenoxaprop or imazamethabenz-SC. A 2 h interval between imazamethabenz-LC application followed by fenoxaprop application overcame the antagonism. The sequence of the split application was important in determining the interaction of these two herbicides. Norstar winter wheat was tolerant to imazamethabenz alone at all rates up to 600 g ha⁻¹ active ingredient (a.i.) but a rate of 600 g ha¹ reduced shoot dry weight of Kyle durum wheat and Katepwa spring wheat. All crop varieties tested were injured by fenoxaprop alone at 100 g a.i. ha⁻¹. Combinations of imazamethabenz and fenoxaprop reduced crop phytotoxicity compared with fenoxaprop alone.