Selective Action of Trifluralin for Control of Green Foxtail in Wheat

Abstract

The selective action of α,α,α-trifluoro-2,6-dinitro- N,N -dipropyl- p -toluidine (trifluralin) for the control of green foxtail (Setaria viridis (L.) Beauv.) in wheat (Triticum aestivum L.) was studied. Seedlings of both species, especially in the early stage of growth, were particularly susceptible to herbicide applied in the region of the coleoptile node. Selective control with trifluralin was possible, however, because of the morphological differences between the seedlings of the two species. Thus, the sensitive coleoptilar node area of green foxtail was located at a depth of less than 1 cm from the soil surface regardless of planting depth. The coleoptile node of wheat remained closely associated with the caryopsis. When a protective band of untreated soil was used to separate the caryopses from a 5-cm band of surface soil containing 1.12 ppmw of trifluralin, the shoot growth of wheat was normal. Much lower rates of trifluralin effectively controlled green foxtail, as surface or subsurface placement of a 1.3-cm layer of soil containing 1.12 ppmw of chemical above the foxtail caryopses completely inhibited shoot development. In addition to the differences in morphological development between the two species, the fact that green foxtail was considerably more susceptible to trifluralin than wheat was considered as an important factor contributing to the selective control.