Kochia Found in Missouri Soybeans

JEFFERSON CITY, Mo. (DTN) -- Kochia, a highly competitive weed well adapted to the Great Plains and western regions of the U.S. and Canada, has made its way to Missouri soybean fields.

Wayne Flanary, University of Missouri Extension field specialist in agronomy, discovered large, scattered kochia plants in soybean fields in Atchison County, Missouri, which borders Iowa to the north and Nebraska to the west. He noted that flooding along the Missouri River and its tributaries likely carried the weed into agricultural fields.

Though the weed species is not new to Missouri, this may be the first report of kochia showing up in cropland in the state, said MU Extension weed scientist Kevin Bradley.

"I have never gotten calls or complaints about this species in corn or soybean fields," said Bradley, who joined the MU faculty in 2003. "I spend time actively looking for these kinds of situations and have never seen it in a Missouri corn or soybean field before."

Kochia can be identified by its alternating arrangement of linear leaves covered with dense hairs. It can grow 6 feet tall and has a spherical shape. Roots can extend 15 feet and measure 21 feet in diameter.

The weed grows rapidly and aggressively outcompetes crops for water, nutrients and sunlight. It's also drought tolerant, producing up to 30,000 seeds per plant. These seeds have potential to germinate quickly -- within two or three hours under the right conditions. As kochia matures, the stem can separate from the root, and the plant becomes a tumbleweed that spreads seeds across fields. Early emerging kochia can reduce crop yields by 70% or more and can also interfere with harvest.

HOW TO MANAGE KOCHIA

The United Soybean Board's Take Action campaign for herbicide-resistance management published a guide for managing kochia in soybeans. It offers the following recommendations:

-- Rotate crops. Crop rotation is important to help diversify kochia-control strategies and herbicide programs over time. A competitive winter wheat crop can greatly suppress kochia emergence and growth.

-- Start clean. Because of kochia's emergence patterns, dense populations and difficult-to-control large plants, it's critical that the weed be controlled early, preferably before or at planting. More effective kochia herbicides are available in grass crops than in broadleaf crops, especially for postemergence control.

-- Apply an effective soil-applied, pre-emergence herbicide. Kochia can be controlled by several residual herbicides if activated before germination. These products should be applied in late fall or very early spring to be activated before kochia starts to germinate. This strategy can reduce the reliance on postemergence herbicides.

-- Target kochia before it grows taller than 3-4 inches. Apply postemergence herbicides with the recommended adjuvants, tank-mix partners, spray volumes and application guidelines to improve efficacy.

-- Prevent seed production. Killing kochia before it flowers and produces seed is an effective way to manage it. Fall cover crops can suppress kochia establishment and outcompete young seedlings in the spring. Tillage is also an option, but it can deplete soil moisture and leaves soil prone to erosion.

The complete kochia management guide is available here: https://extension.missouri.edu/….

KOCHIA CONCERNS

Across the Great Plains, in states such as Kansas, Nebraska and the Dakotas, kochia drives weed-management decisions. While the appearance of a weed in a new locale also isn't new (think Palmer amaranth moving north and east), the bigger concern is that kochia may already be herbicide resistant. The International Herbicide-Resistant Weed Database documents populations of kochia that are resistant to up to four modes of actions.

"Growers should keep in mind that they may already be dealing with a population that is resistant to glyphosate or perhaps some other herbicide," Bradley said. "There are numerous types of herbicide-resistant kochia populations in these states, including populations with resistance to the triazines (group 5 herbicides), to glyphosate and even some populations with resistance to dicamba."

The weed scientist suggested spot spraying and hand rogueing the scattered plants that were found in Atchison County. Farmers who suspect they may have kochia in their fields should contact their local MU Extension agronomist.

Jason Jenkins can be reached at jason.jenkins@dtn.com

Follow him on social platform X @JasonJenkinsDTN

(c) Copyright 2025 DTN, LLC. All rights reserved.