Increasing efficacy of graminicides with a forward angled spray

Abstract

Control of annual grass species with vertically oriented leaves in agricultural crops by application of foliar acting herbicides with conventional hydraulic sprayers can be increased using forward angled nozzles. Changing the spray angle from the normally predominantly vertical spray towards an angled spray increases the potential target size of vertically oriented targets. This theory was tested in field experiments from 2005 to 2009 investigating control of three different grass species and a dicotyledonous weed species at early growth stages using foliar acting herbicides. Lolium perenne and Alopecurus myosuroides are annual grasses with a predominantly vertical habit whereas Apera spica-venti and Brassica napus are species with more horizontally oriented leaves at growth stages where applications were carried out. Using a 60° forward angled spray resulted in large increases in herbicide efficacy on L. perenne at early growth stages using nozzles with different spray quality, at different driving speeds and in different wind conditions. Similarly graminicide efficacy was increased when nozzles were angled 60° forward controlling A. myosuroides. Experiments investigating control of the two species with a more horizontal habit, A. spica-venti and B. napus, gave no significant difference between results with standard and angled applications.