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Title: APPLICATION TIMING EFFECTS ON PERSISTENCE AND BIOEFFICACY OF CHLOROACETAMIDE HERBICIDES

Author
item PARKER, DANIEL - UNIV OF ILLINOIS
item SIMMONS, FREDERICK - UNIV OF ILLINOIS
item WAX, LOYD

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 3/17/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Early preplant applications of chloroacetamide herbicides are used to spread applicator work load and to increase the probability of receiving rainfall prior to weed seed germination. This research was initiated to evaluate the persistence and efficacy of five herbicides over several application timings ranging from fall to preplant. The study was conducted in 1998 and 1999 at Annawan, DeKalb, and Dwight, IL. The racemic mix and active isomer of metolachlor, acetochlor, and two encapsulated formulations of acetochlor were evaluated at five application timings including fall, 60 and 30 (EPP) days before planting, preplant incorporated (PPI) and pre-emergence (PRE). Application rates for all but the fall application timing were; racemic mix of metolachlor, 2.8 kg ha-1, the active isomer of metolachlor, 1.8 kg ha-1 and acetochlor formulations, 2.2 kg ha-1. Fall application rates were increased by 25% for all herbicides. Control of giant foxtail (Setaria faberi L.) was evaluated at 30 and 60 (DAP) days after planting. Two soil samples (17-cm2 and 6-cm deep), were taken from each plot 1 to 2 weeks after planting, and a greenhouse bioassay was conducted using giant foxtail. Herbicide efficacy was visually rated and giant foxtail dry weights were measured at 21 DAP.PRE and PPI application timings provided the best control of giant foxtail, and all herbicides performed similarly at these application timings. The metolachlor formulations and MON58430, an encapsulated formulation of acetochlor, provided approximately 20% or more control than the two other acetochlor formulations in the fall and 60 EPP timings. At the 30 EPP timing, non-encapsulated acetochlor provided at least 15% less control of giant foxtail than all other herbicides.