Fall and Early Preplant Application Timing Effects on Persistence and Efficacy of Acetamide Herbicides¹

Abstract

The persistence and efficacy of acetamide herbicides at application timings from fall to preemergence (PRE) were studied in 1998 and 1999 on mollisols (1.1 to 2.8% organic carbon). Metolachlor, s-metolachlor, acetochlor (as an emulsifiable concentrate [EC] formulation and two encapsulated formulations, capsule suspension [CS] and microencapsulated [ME]), and the combination of flufenacet + metribuzin were evaluated at five application times including late fall, 60 and 30 d early preplant (EPP), preplant incorporated, and PRE. Soil bioassays 180 d after application indicated flufenacet + metribuzin, metolachlor, s-metolachlor, and the acetochlor CS had 62 to 74% giant foxtail control, whereas acetochlor EC and ME had 43 to 46% control. Applications at 60 EPP of metolachlor, s-metolachlor, and acetochlor CS provided 70 to 75% giant foxtail control in greenhouse bioassays, whereas flufenacet + metribuzin, acetochlor ME, and acetochlor EC provided 38 to 57% control. At the 30 EPP timing, metolachlor and acetochlor CS had 80 to 82% control, whereas acetochlor EC provided 46% control, and acetochlor ME, flufenacet + metribuzin, and s-metolachlor had 65 to 74% control. Quantitative soil analysis (0 to 6 cm) 10 d after planting (DAP) indicated metolachlor, s-metolachlor, and acetochlor CS concentrations ranged from 12 to 16% and 32 to 47% of applied herbicide for the fall and PRE application timings, respectively, whereas acetochlor (ME and EC) were from 1 to 3% and 16 to 21% of applied for the fall and PRE application timings, respectively. Bioassay reduction was correlated (R 2 = 0.68) with soil-herbicide concentrations at 10 DAP.

Weed Control and Peanut (Arachis hypogaea L.) Response to Acetochlor Alone and in Combination with Various Herbicides

“…A microencapsulated (ME) formulation of acetochlor recently received registration for PPI, PRE, and POST application in peanut (Anonymous 2017b). In addition to improving crop safety, this formulation of acetochlor extends herbicide persistence in the soil compared with the emulsifiable concentrate formulation (Parker et al, 2005;Scher et al, 1998). Grichar et al (2015) reported no negative effect of acetochlor ME application timing and rate on peanut grade and yield in runner and Spanish market type cultivars.…”

Environmental fate of S-Metolachlor: a review

“…Depending on crop and variety, S-metolachlor can be applied in preplant incorporated (PPI), preemergence (PRE) or early postemergence (EPOST) of tolerant plant species with minimal crop injury under certain conditions (Parker et al, 2005;Senseman, 2007;Bollman et al, 2008). Crop tolerance has been attributed to the ability of plants to rapidly metabolize S-metolachlor by detoxification reactions, preventing accumulation at phytotoxic levels in plant cells .…”

Residual Herbicide Dissipation in Vegetable Production

“…Other studies came to the same conclusions and also indicated that metolachlor binding was by physical forces between metolachlor molecules and soil constituent surfaces (Weber et al, 2003). Half-life of metolachlor varies with soil temperature, moisture, and organic matter content (Parker et al, 2005;Vencill, 2002 a). Previous research indicated that the adsorption and mobility of sulfentrazone is pH and soil type-dependent and that it does exhibit hysteresis (Grey et al, 2000).…”

“…The residual effects of sulfentrazone on rotational cotton have been established with rates exceeding 0.4 kg ha -1 applied the previous year (Main et al, 2004;Ohmes et al, 2000). Persistence, dissipation, and degradation of halosulfuron (Kuwatsuka & Yamamoto 1997a, metolachlor (Gaynor et al, 1993, Parker et al 2005Weber et al, 2003), and sulfentrazone (Grey et al, , 2000Ohmes et al, 2000;Reddy & Locke, 1998) have been previously investigated in agronomic and/or vegetable soils. These investigations emphasized soil and/or organic cover scenarios in separate experiments.…”