Prickly lettuce was one of the first weeds to show documented resistance to ALS herbicides over 20 years ago. Photo credit: AgStock Images / Joe DiTomaso
More than 20 years ago, cereal growers across the Northern Plains became painfully aware of the first documented ALS herbicide-resistant weeds: kochia, Russian thistle and prickly lettuce. The problem began slowly and advanced to plague the predominantly cereal-growing region, as nearly 90 percent of growers at the time relied solely on ALS-inhibitor herbicides for their weed control.
Once resistant weeds prevailed, ALS (Group 2) chemistry quickly lost its effectiveness. Four to five years of repeated use in continuous wheat resulted in widespread nonperformance.
Experts recommended implementing diversified practices such as crop rotation, mechanical tillage and the application of herbicides with different, effective sites of action from different classes of chemistry to avoid selecting for ALS-resistant weed biotypes.
Growers still get a lot of use out of ALS herbicides. They simply need to combine them in tank mixes with effective chemistries that target specific problem weeds.
Experts recommend that in addition to cultural practices, weed control strategies should include the following:
- Apply burndown and pre-emergence residual herbicides using chemistries with different, effective modes and sites of action
- Control weeds with postemergence herbicides when they are small, ideally before they reach 3 to 4 inches in height
- If weeds do escape because of timing or wet weather, additional postemergence herbicide applications may be needed
Now that resistance to ALS herbicides, glyphosate, dicamba, triazines and others has been documented, today’s standard for managing resistant weeds is using integrated weed management practices. This means not allowing any weed to go to seed and remain viable in the soil seedbank for years to come.
Increased management through practices such as crop rotation in combination with careful selection of effective herbicides to control resistant weeds is key. As a last resort, hand weeding a few escaped weed biotypes to prevent seed production can be an effective method to prevent further resistant development.
Bayer Weed Management Solutions in Cereals
Bayer offers a broad portfolio of herbicides to control tough-to-manage and resistant weeds in cereals, including Huskie® (6, 27) in both winter and spring wheat, Wolverine® Advanced (1, 6, 27) in spring wheat, and Varro® (2) in both spring and durum wheat.
In addition, Huskie® Complete herbicide** (2, 27, 6) is a spring wheat solution and features ALS grass control of key weeds including wild oats, yellow foxtail and green foxtail.
A well-thought-out herbicide program, using multiple sites of action and nonchemical practices, should be implemented.*
To learn more about using herbicides with effective modes of action, see the Herbicide Resistance Management Guide. View Bayer’s product portfolio to learn more about weed control from Bayer or contact your local Bayer representative.
* Always read and follow label instructions. Not every product is suitable for every situation, nor registered in every state, and proper application techniques will enhance results. Before applying any herbicide, please read the entire label for the best possible results and to confirm that the product is effective on the weeds you wish to control.
** Huskie Complete is a Restricted Use Pesticide.