Top Crop Manager

Soil active herbicides help manage weed resistance

August 27, 2021  By Stefanie Croley

Soil active herbicides are a great addition to any weed management program. By reducing weed pressures early on, crops can get off to a strong start in the spring. With different active ingredients and application timings, soil active herbicides can help tackle troublesome resistant weeds and slow down the development of herbicide resistance.

Graham Collier doesn’t mince words when he talks about herbicide resistance. “We have a serious problem in Western Canada,” says the Portfolio Manager for Nufarm Canada.

Canada currently ranks third in the world—behind only Australia and the United States—for cases of herbicide resistance. This means farmers in western Canada should plan their herbicide application strategy around managing resistance.

“If you are going to use herbicides on your farm, you have to expect that you will be selecting for resistance to those herbicides,” says Collier. “Over time, you remove the highly susceptible individual weeds and select for the ones that are tolerant for some reason, whether those weeds are truly resistant because of a physiological change or resistant in another manner.”

While we can’t prevent herbicide resistance, we can slow resistance development. It’s important that we continuously rotate crops, rotate herbicide application timing, rotate modes of action, rotate active ingredients, scout for surviving weeds and keep records. Soil active herbicides are an excellent addition to a resistance management strategy.

How soil active herbicides work
Valtera™ and Fierce® soil active herbicides are great tools to help slow down weed resistance. They can be applied with a field sprayer in the fall after harvest and just before freeze up or soon after spring thaw. Valtera and Fierce provide up to eight weeks of early season control helping your fields stay clean as you seed your crops and allowing them to get off to a strong start without weed competition.

Once sprayed, the herbicide sits on top of the soil. It activates and moves into the soil water solution with moisture from snowmelt (if applied in fall) or spring rainfall (if applied in spring). The herbicide remains effective in the soil water solution for up to eight weeks providing a layer of protection just below the soil surface. As weeds germinate and grow through that soil layer, they come into contact with the herbicide molecules in the soil water solution. Both Valtera and Fierce help eliminate tough-to-kill weeds before they have a chance to get established and compete with your crops.

“Valtera and Fierce will not control weeds that have already germinated so remember to tank-mix with glyphosate and a burndown partner like BlackHawk and GoldWing.” – Graham Collier

Add Valtera and Fierce to your resistance management toolbox
Valtera and Fierce provide up to eight weeks of weed control after activation to help manage early or late flushing weeds that have adapted their growth cycle based on historical practices. Remember weeds are smart and like routine, so changing up your application timing is one way to help slow resistant and adaptive populations.


Another benefit of Valtera and Fierce is that they contain unique active ingredients for residual early season control. Valtera contains flumioxazin (Group 14) to manage broadleaf weeds like chickweed, kochia, lamb’s quarters, pigweed and many more, while Fierce is made up of flumioxazin (Group 14) and pyroxasulfone (Group 15) for control of both broadleaf and grass weeds like green foxtail and wild oats (suppression). These products provide additional options that allow farmers to rotate herbicide groups and fight tough weeds in their fields.

Protecting fields early in the season with unique active ingredients can help make in-crop herbicide applications more effective and preserve their longevity. Weeds that germinate and escape in the spring will generally be smaller, less competitive, and more susceptible to an in-crop herbicide application. This helps reduce the amount of weed seed set back into the seedbank for future years. Reducing the overall weed population also means more moisture and nutrients for crops during critical growth stages and less green material during harvest.

So, if you have some challenging weeds, and you haven’t already started, it’s time to change it up with a soil active herbicide application this fall or early next spring. Help your pulse, soybean and wheat crops start clean next season with Nufarm. Learn more by visiting Nufarm.


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