Glyphosate-resistant kochia has been documented in many locations in central ND. The following web site announces documentation of glyphosate-resistant kochia in Montana. This discouraging announcement is another indication that this biotype may spread very rapidly across the entire plains and northern plains region. This will also require a very aggressive and creative management program in the coming years.
Now that wheat harvest is nearing completion, glyphosate-resistant kochia may show up after preharvest glyphosate applications in wheat stubble. To reduce problems in next year’s crop, especially if it will be a glyphosate resistant crop, extra effort will be required. Since kochia seed has very little dormancy, aggressive management will likely deplete the seed bank making management in soybeans and other crops easier.
Effective herbicides in wheat stubble may include products that contain bromoxynil (Bronate and several others), or dicamba. The herbicide 2.4-D is generally not very effective.
The current drought conditions may reduce herbicide activity, but adding an aggressive oil adjuvant (MSO type) and nitrogen fertilizer may increase weed control. These herbicides may or may not restrict planting of cover crops depending on the species chosen for planting.
The following is a question we received: We have been getting questions on whether the escaped kochia is resistant to glyphosate. There is a chance the kochia might be resistant when talking to growers about their weed control plans that are used on some fields. What or where do I need to send samples? This is mainly glyphosate that growers are concerned about.
Answer: Sending seed or plant material to get tested for resistance will cost considerable money. Many have emailed with the same request.
In short, we have documented glyphosate-resistant kochia in many locations across ND. Since it has already happened in ND and you see general nonperformance or escapes then the best plan is to assume that the resistant biotype has developed in your area, your growers have it, and will require everyone to devise appropriate and sustained control strategies for the next several years. From the rapid spread of kochia that we have observed this summer it is a matter of not “if” but “when” most of the state will have this problem. This, for sure, will be the most important weed pest we will confront and will require the most creative and effective weed management ever designed.
A company in Canada called Agquest does testing for herbicide resistance. See the bottom of page 103 in the weed guide.
View regional maps summarizing current observations in
Wheat and Barley