Submitted to: Research Report North Central Weed Science Society United States
Publication Type: Other
Publication Acceptance Date: 12/8/1999
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: The objective of this research was to evaluate various soil-applied and postemergence herbicides for control of kochia in soybean. The study was established on a producer's field near Hoopeston, Illinois. The soil was a Flanagan silt loam with a pH of 6.1 and 3.5% organic matter. Asgrow 3601 soybean was planted in 8 inch rows at 180,000 plants per acre on May 10, without prior tillage. Prior to planting, the entire study area received an application of glyphosate plus pendimethalin to control existing vegetation. Treatments were arranged in randomized complete blocks with four replications of plots 10 by 30 feet. Herbicides were applied with a CO2 backpack sprayer delivering 20 gpa and equipped with 11003 flat fan nozzles. Soybean tolerance to all soil-applied herbicides was excellent at each evaluation timing. Soybean tolerance to postemergence herbicides varied. Lactofen, acifluorfen, and fomesafen caused the greatest injury 10 days after application. ICIA-0224 and imazamox also caused significant crop injury 10 days after application. By 30 days after application, little soybean injury was present from any postemergence herbicide treatment. Clomazone provided excellent control of kochia and was the only soil-applied herbicide that afforded greater than 90% kochia control by 30 days after application. Postemergence herbicide treatments varied greatly in the level of kochia control. Glyphosate and ICIA-0224 treatments provided 94% or greater control of kochia 30 days after application regardless of application rate. Imazethapyr or imazamox provided 27% or less control of kochia 30 days after application, suggesting this kochia population may be resistant to these acetolactate synthase inhibiting herbicides.