Control of Italian Ryegrass and Wild Oats in Winter Wheat with HOE 234081

Abstract Italian ryegrass (Lolium multiflorum Lam.) and wild oats (Avena fatua L.) are widespread and competitive weeds in winter grain fields of western Oregon and Washington. A new herbicide, HOE 23408 {methyl 2‐[4‐(2,4‐dichlorophenoxy) phenoxy] propanoate}, has shown promise for selective control of both species. Field studies were conducted at 12 locations in 1974–75 and 1975–76 to evaluate the effectiveness and consistency of weed control with HOE 23408 in winter wheat (Triticum aestivum L.) and to measure the influence of removing ryegrass and wild oats on wheat grain yields. HOE 23408 was applied preemergence, early postemergence (two to three‐leaf stage), and late postemergence (tillering stage) at rates from 0.84 to 2.24 kg/ha. When applied preemergence, HOE 23408 gave adequate control of ryegrass when the seedbed was relatively free of clods and plant residues but wild oat control was erratic. Nearly complete control of both species was obtained from all postemergence treatments at rates as low as 0.84 kg/ha. Increases in wheat grain yield were often dramatic; in one case, the increase over the untreated control was 6,000 kg/ha from treatment at 1.12 kg/ha applied early postemergence. Average yields from this treatment exceeded yields from plots treated with diuron [3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea], barban (4‐chloro‐2‐butynyl m‐chlorocarbanilate), and triallate [S‐(2,3,3‐trichloroallyl) diisopropylthiocarbamate] by 2,170, 1,280, and 1,580 kg/ha, respectively. Results indicate that HOE 23408 has considerable potential for control of ryegrass and wild oats and that large increases in yield of wheat grain can be expected when severe infestations of these weeds are controlled.