Back to Blog Agronomy

Part 6: Management Strategies for Difficult-to-Control Weeds (Driver Weeds) in Soybeans

December 2019 

Last in our series of difficult-to-control driver weeds, we discuss kochia (a.k.a. tumbleweed). Kochia can be found in most regions throughout the United States and into Canada and can spread rapidly. From ditches to fences to cropland, kochia’s ability to transfer seed wherever the wind takes it and its broad adaptability mean this pesky weed can wreak havoc on growers’ yields. Learn more about the strengths and weaknesses of kochia and control tactics for this driver weed.

The Bad News (Strengths)

  • Kochia has a high rate of pubescence, or “hair covered” leaves, which makes it difficult for herbicides to stay on the leaf long enough to be absorbed.
  • It is also extremely bushy, with numerous branches that develop a heavy canopy, making coverage of leaf surface difficult.
  • Kochia can reach up to six-feet high and have roots that can extend as much as 15- feet below the soil surface. This makes kochia extremely competitive with other plants in its environment. In fact, according to experts, kochia can reduce yields by up to 70 percent or more.
  • Kochia is prone to cross pollination, allowing herbicide-resistant biotypes to pollinate herbicide-susceptible biotypes, leaving the prodigy resistant. This evolutionary advantage, as well as the “tumbleweed” aspect of the plant, allows these resistant biotypes to spread quickly and over long distances.
  • In addition to blowing with the wind, as tumbleweeds, kochia can hitch rides on vehicles, travelling from the western Corn Belt areas to central and eastern Corn Belt areas while leaving seed along its path.

The Good News (Weaknesses)

  • Kochia seed is viable in the soil for only a short time; however, initial germination rates are high and can range from 89 to 93 percent.
  • Kochia seed typically emerges early for a summer annual, in soil temperatures ranging from 37–46° Fahrenheit. The early emergence makes kochia easier to control with cover crops and early spring pre-emerge herbicides.
  • Germination is greater in shallow seed depths and decreases as soil depth increases.   

Management Strategies

*Note: Current known herbicide resistance includes Groups 5 (triazines), 9 (glyphosate), 2 (ALS) and 4 (synthetic auxins). There is some known cross resistance (single population) to both Groups 5 and 2.

  • Know your resistance profile. Have your population tested to know what herbicides will be effective.
  • Start clean. Consider tillage and/or an effective burndown control that eliminates actively growing weeds.
    • Tillage is the most effective but is not a viable alternative in all areas of the country because of erosion concerns and moisture loss.
    • Consult your local agronomist or university extension office for specific burndown recommendations.
  • Utilize an effective soil-residual herbicide. Using these products in multiple sequential applications is encouraged where possible to delay and diminish the germination and emergence of kochia to allow soybeans a competitive advantage in row closure, canopy and plant density.
  • Utilize an effective post-herbicide program. Apply an effective post-herbicide application(s) for pre-escapes.
  • Narrow-row soybeans. In some cases, narrow-row soybeans may be warranted to increase photosynthetic competitiveness and decrease kochia growth habits.
  • Cover crops. In some cases, cover crops have shown an increased ability to lessen weed seed bank populations and delay emergence.
  • Manual eradication. In severe infestations, manual eradication may be necessary for a few years to get the population under control.
  • Harvest eradication. In cases in the South, growers have turned to adding mechanical seed destroyers on their combines to control weed seed escapes.
  • Conventional herbicide system. Using a conventional herbicide system that relies on multiple, timed passes with soil-applied residuals and effective post-applied herbicides with current broad spectrum herbicides can be an effective strategy. This system is generally costly; however, the increase in yield from reducing weed competition generally outweighs the cost of treatment.

Trait System Usage

Use trait systems that provide the ability to apply multiple effective modes of action simultaneously to combat herbicide resistance.  For instance, Enlist E3® system allows the use of Enlist One® with 2,4-D choline to be applied with both glyphosate and glufosinate and additional tank mix partners to eliminate and delay further kochia emergence. This system combines many of the strategies discussed into a flexible platform.

To learn more about kochia and how to manage this hard-to-control driver weed on your farm, contact your local Stine agronomist or university extension specialist.

Resources and Citations:

Kochia
https://iwilltakeaction.com/weed/kochia

Kochia Management in Soybeans
https://iwilltakeaction.com/uploads/files/57229-7-ta-hrm-factsheet-kochia-r2-lr-final.pdf

Kochia
https://ohiostate.pressbooks.pub/ohionoxiousweeds/chapter/kochia-section/