5 Keys to Managing Kochia in Soybeans

Ranked No. 7 on the Top 10 Most Troublesome Weeds, kochia is well adapted to the Great Plains and western regions of the U.S. and Canada because it is tolerant to hot, dry conditions and soils with high salinity, according to a Fact Sheet published on the University of Missouri Weed Science website. In addition, the evolution of herbicide-resistant kochia is rapid due to high genetic diversity, short seed life, and heavy reliance on herbicides for control in minimum- and no-till cropping systems. Here are five keys to managing kochia:

1. Rotate crops. Crop rotation is important to help diversify kochia-control strategies and herbicide programs over time. More effective kochia herbicides are available in grass crops than in broadleaf crops, especially for postemergence control. A competitive winter wheat crop can greatly suppress kochia emergence and growth.
2. Start clean. It is imperative to control kochia in early spring because of its emergence patterns, dense populations and difficult-to-control large plants. Kochia should be controlled at or before planting. Very few effective postemergence herbicides are available for kochia control in broadleaf crops.
3. Apply an effective soil-applied, pre-emergence herbicide. Kochia can be controlled by a number of residual herbicides if activated before germination. Residual herbicides should be applied in late fall or very early spring to be activated before kochia starts to germinate. Early season control with pre-emergence residual herbicides greatly reduces the reliance on postemergence herbicides for control.
4. Target small weeds after they emerge. Timing of the herbicide application is critical for postemergence control of kochia. To optimize herbicide performance, apply postemergence herbicides with the recommended adjuvants, tank-mix partners, spray volumes, and application guidelines before kochia grows taller than 3-4 inches.
5. Prevent seed production. Kochia is day-length sensitive and begins flowering in late July and August. Due to its short seed life, killing kochia before it flowers and produces seed is an effective way to manage it. Strategic tillage and cover crops might be helpful in minimizing kochia seed production. Fall cover crops can suppress kochia establishment and out-compete young seedlings in the spring. Tillage controls kochia by disrupting the roots and dehydrating plants, but it also depletes soil moisture and leaves soil more vulnerable to wind and water erosion.