Activity of Selective Postemergence Grass Herbicides in Soil

Abstract

Several herbicides were toxic to barnyardgrass [Echinochloa crus-galli(L.) Beauv. # ECHCG] when applied as a soil treatment at 0.56 kg ai/ha to a sandy loam soil with 0.8% organic matter. At this application rate, haloxyfop {methyl ester of 2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, CGA-82725 {2-propynyl ester of 2-[4-[(3,5-dichloro-2-pyridinyl)oxy] phenoxy] propanoate}, and DPX-Y6202 {ethyl ester of 2-[4-[(6-chloro-2-quinoxalinyl)oxy]-phenoxy] propanoate} provided the greatest persistence of activity. At 31, 28, and 25 days after treatment with these herbicides, respectively, barnyardgrass growth was still inhibited by 50%. Soil activity and persistence of fluazifop {butyl ester of (±)-2-[4-[[5-trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} increased following soil sterilization. Covering the soil surface with vermiculite prior to treatment intercepted the spray and significantly reduced control of 4- to 6-cm-tall barnyardgrass plants with fluazifop.