Published online by Cambridge University Press: 12 June 2017
Over-the-top applications of metriflufen {2-[4-(4-trifluoromethylphenoxy)phenoxy] propanoic acid} at 0.6 to 2.2 kg/ha were highly toxic to johnsongrass [Sorghum halepense (L.) Pers.], but caused little visual injury to soybeans [Glycine max (L.) Merr. ‘Hill’]. Directed applications of metriflufen at 0.8 to 3.4 kg/ha provided equal and, in a few comparisons, better control of johnsongrass than did some rates of the herbicide applied over-the-top. Application of metriflufen at 0.8 and 1.7 kg/ha in directed sprays resulted in higher soybean yields than did comparable treatments applied over-the-top; yields of directed vs. over-the-top applications of metriflufen at 3.4 kg/ha resulted in statistically equal soybean yields. The research suggested that metriflufen entered johnsongrass plants through shoots and leaves and also through roots. Johnsongrass control was excellent following applications of metriflufen at 1.7 and 2.2 kg/ha without soybean injury and with greatly increased soybean yields. Results following over-the-top applications of metriflufen at 1.1 kg/ha to ‘Hill’, ‘Tracy’, ‘Lee 68’, ‘Bragg’, and ‘Forrest’ soybeans at three different stages of morphological development did not demonstrate any appreciable differences in the response of the cultivars to the herbicide.