DINITROANILINE HERBICIDES FOR GRASSY WEED CONTROL IN RAPESEED

Five substituted dinitroaniline herbicides applied as preplanting soil incorporation treatments were evaluated in six field experiments in 1971, 1973, and 1974 for controlling green foxtail (Setaria viridis (L.) Beauv.) and wild oats (Avena fatua L.), and for tolerance of rapeseed (Brassica campestris L. and B. napus L.). In these experiments, A-820 (N-sec-butyl-4-tert-butyl-2,6-dinitroapiline) had the least activity, while dinitramine (N4,N4-diethyl-α,α,α,-trifluoro-3,5-dinitrotoluene-2,4-diamine) had the greatest activity, and in some tests injured germinating rapeseed, resulting in thinned stands and reduced yield. The activity of fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoro-methyl) aniline] and profluralin [N(cyclopropyl-methyl)-α,α,α-trifluro-2, 6-dinitro-N-propyl-p-toluidine] was slightly weaker than that of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine). All these herbicides gave good control of green foxtail and wild oats. In 1971, due to low populations of green foxtail, good weed control did not give rapeseed yield increases. In 1973, under normal climatic conditions, rapeseed yields were increased significantly when the application of dinitramine, fluchloralin, profluralin, and trifluralin controlled green foxtail and wild oats successfully. In 1974, under drought conditions, good weed control from four dinitroanilines and triallate [S-(2,3,3-trichloroallyl) diisopropylthiocarbamate] was not reflected in significant yield increases although profluralin gave a significant yield increase in one test. Disc soil incorporation (7.5–10 cm deep) of dinitramine and trifluralin gave slightly better weed control and higher, though not significant, yield increases than harrow soil incorporation (2.5–5 cm deep).