Glyphosate Resistant Kochia (kochia scoparia) Management.

Kochia infests Kansas crops annually often requiring herbicide applications to effectively management the problem.  Kansas kochia populations have developed resistance to several herbicide modes of action including triazines and ALS inhibitors.  A Stevens County, KS kochia population survived 0.75 lb ae glyphosate in greenhouse work was reported in 2008 at NCWSS.  Since that time, glyphosate resistant kochia is wide spread across the western half of Kansas.  Glyphosate resistance has complicated kochia management in crop production in Kansas.  Dillie et.al. reported that at several locations across KS, CO, WY, and NE, kochia begin emerging in March and that 90% of the kochia had emerged by late April.  Personal observation suggests that many problems associated with unsuccessful control of glyphosate resistant kochia are linked to inadequate control of the initial dense kochia canopies which develop from March and April emerged kochia.  Experiments were established in 2011 and 2012 to evaluate the effectiveness of herbicides applied in March preemergence to kochia for managing heavy kochia populations.  Surface applied residual herbicides which effectively controlled early germinating kochia include, dicamba, atrazine, metribuzin, sulfentrazone, isoxaflutole, and various combinations of these herbicides.  Additional experiments suggest that several herbicide programs involving the previously discussed herbicides applied preemergence in corn, sorghum, or soybean and postemergence in corn and sorghum controlled kochia especially following an effective early preplant March treatment.  Growers can manage glyphosate resistant kochia, however it will involve March applied herbicides prior to kochia emergence, preemergence herbicides at crop planting, followed by effective postemergence herbicides.  These effective programs will result in increased cost of production of crops grown in western Kansas.