Phytotoxicity and Soil Activity of HOE 23408

Abstract

Greenhouse and field studies were conducted to compare the phytotoxicity of HOE 23408 {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy]-propanoate} to several crops and annual grass weeds, and to determine the herbicides's soil mobility and persistence. In general, the order of susceptibility of 13 seedling grassy weeds remained constant, whether the herbicide was applied preplant incorporated, pre-emergence, or postemergence. The herbicide was most phytotoxic when it was applied either preplant incorporated or early postemergence. Grain sorghum [Sorghum bicolor(L.) Moench ‘BR-54′] and oats (Avena sativaL. ‘Cimarron’) were moderately susceptible to HOE 23408, whereas barley (Hordeum vulgareL. ‘Will’) exhibited marginal tolerance. Wheat (Triticum aestivumL. ‘Triumph 64′) and cotton (Gossypium hirsutumL. ‘Westburn 70′) showed tolerance to HOE 23408 at rates up to 6 ppmw, and soybean [Glycine max(L.) Merr. ‘Bragg’] and peanut (Arachis hypogaeaL. ‘Spanhoma’) demonstrated tolerance to concentrations as high as 24 ppmw. The soil mobility of HOE 23408 was similar to that of trifluralin (a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine). No soil phytotoxicity was found 8 weeks after herbicide application in the field or under laboratory incubation conditions of 5 or 10% soil moisture at 21 C. Dissipation was much slower at a temperature of 4.4 C, regardless of the soil moisture level.