Things You'll Need
Tillage and spraying equipment
Kochia, or Kochia scoparia, is an annual broadleaf weed that spreads rapidly once it goes to seed. Mowing is effective in controlling the weed when it is small, but herbicides are often required for larger plants. Kochia is a native of Europe and was introduced into North America as an ornamental plant. The weed assumes a bright red color during later summer and fall and is commonly referred to as fireweed. You can use both postemergence and preemergence herbicides, or mechanical methods to control kochia.
Till the soil well early in the season. Soil tillage is among the most effective control of kochia, since the seed germination that takes place at this time is disrupted, according to the University of Illinois Extension Service. Tillage controls both the seedlings and larger plants.
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Use sulfentrazone as a preemergence herbicide for kochia control, as cited by the Montana State University Extension Service.
Apply products containing sulfentrazone to the soil to inhibit germination of seed. Sulfentrazone is more effective in soils with higher pH. You will need to add higher rates of the herbicide in fine-textured soil and in soils that are rich in organic matter. Irrigate the ground well with alkaline water after applying herbicide.
Use products containing glyphosate for the postemergence control of kochia, as indicated by the University of Illinois Extension. You can also use products containing dicamba for the postemergence control of the weed.
Apply glyphosate at the recommended rate on weeds that are less than four inches in diameter. Using the chemical at lower rates on larger weeds will often require repeat applications.
Every kochia plant produces thousands of seeds that have a very high rate of germination under optimal growth conditions. For best control, start to apply herbicides or use mechanical means of controlling the weed before it goes to seed.
Glyphosate is a nonselective herbicide and will damage all plants that it comes in contact with. Use the chemical carefully if you are trying to kill kochia growing between desired plants. Avoid using chemicals on windy days to minimize chances of drift. Glyphosate products are sold under different trade names. Follow manufacturer's directions for rates of application, and heed safety warnings.