An Evaluation of Herbicides for Control of Wild Oats in Barley: Efficacy, Phytotoxicity, and Barley Variety Susceptibility Studies

Abstract

The control of wild oats (Avena Jatua L.) in Alaskan spring-planted barley was investigated in a series of experiments conducted from 1981-1984. Rates and times of applications of triallate (a preemergence, soil-incorporated herbicide), diclofop, barban, and difenzoquat (postemergence herbicides) were investigated in relation to control of wild oats and barley yield in 1981-1982. Because of very high wild oats populations. none of the herbicides controlled wild oats to the point of· allowing a barley harvest. Generally, wild oats were best controlled when herbicides were applied at an early growth stage and at the highest application rates. Control of wild oats with triallate was the same whether incorporated using parallel or perpendicular passes of a spike-tooth harrow. In 1983-84 both single herbicide treatments and combinations of herbicides were studied. Barban, diclofop, and difenzoquat were applied alone or with triallate applied in the fall or spring in emulsifiable concentrate or granular formulation. Wild oats population levels were lower in these 2 years, and applications of even single herbicides provided good wild oats control. Of the individual herbicides, diclofop provided the best control of wild oats. In general, when triallate was applied in conjunction with diclofop, barban, or difenzoquat, control of wild oats was better and higher barley yields were obtained than when a single wild oats herbicide was applied. When triallate was applied in the fall, the granular formulation provided better control of wild oats than the emulsifiable formulation. In a study of the response of eight barley varieties ('Eero', 'Paavo', 'Galt', 'Otra', 'Otal', 'Datal', 'Udal', 'Weal') to high rates and late times of application of the four herbicides, none of the varieties were differentially susceptible. Diclofop decreased heights of all varieties and decreased test weights.