MANHATTAN — A Kansas State University weed specialist says farmers should be on the lookout for early-emergence of a troublesome weed that competes with farm crops for nutrients, water and light. 

Sarah Lancaster said kochia is among the first summer annual weeds to emerge in the spring. In 2024, kochia was found as early as Feb. 7, following a snowstorm in late January, and temperatures that hit the 50s and 60s in early February – conditions that were very similar to what much of Kansas experienced this year, as well. 

“Early-emerging kochia seedlings use the limited spring soil moisture in dryland production fields,” said Lancaster, noting that good control of the first dense flush of kochia is essential for obtaining a good crop yield later in the season. 

Lancaster said that kochia seedlings emerge in dense populations, which makes adequate herbicide coverage difficult. In addition, glyphosate-resistant kochia is prevalent across western Kansas.

“For these reasons, it is important to apply pre-emergence herbicides in late winter or early spring to control kochia before it emerges,” Lancaster said. 

According to Lancaster, an herbicide program needs two components in order to successfully manage kochia:

• A very soluble and effective herbicide that can be incorporated with very little precipitation, such as dicamba.

• A herbicide that has longer residual activity, which will require perhaps ¾ inches or more precipitation for adequate incorporation, such as atrazine. 

“Precipitation events during late winter are often too small to activate longer-lasting residual herbicides, but dicamba may control kochia for 4-6 weeks until atrazine is incorporate,” Lancaster said.

For those reasons, the best time to apply herbicides is generally January through the first week of March, according to Lancaster. 

Other herbicides with good pre-emergence kochia activity include mesotrione, metribuzin, saflufenacil (Sharpen) and sulfentrazone. Lancaster urges farmers and herbicide applicators to check product labels for crop-specific planting intervals. 

More information on controlling kochia and many other weeds is available in a recently released publication from the K-State Research and Extension bookstore, Chemical Weed Control for Field Crops, Pastures, Rangeland and Noncropland. Farmers can also get information at local extension offices in Kansas.