Herbicide Pre-mixtures Containing Fluroxypyr - Help or Hindrance?

There are many beneficial aspects of herbicide pre-mixtures, such as providing a broader spectrum of weed control; having fewer herbicide containers which reduces storage requirements and means handling one jug instead of two or more; the mix allows for synergistic weed control, reduces time loading the sprayer, usually costs less, and includes specific adjuvants to improve weed control.

With kochia resistant to so many herbicide sites of action, knowing the concentration of each active ingredient in a pre-mixture is more important than ever before!

One example is herbicide pre-mixtures containing fluroxypyr (such as Huskie FX). Currently, there are at least 31 herbicide pre-mixtures containing fluroxypyr labeled in North Dakota for control of kochia in hard red spring wheat.

Many farmers don’t know how much active ingredient is in a pre-mixture and sometimes hardly know which active ingredients are included in the pre-mixture. A former University of Illinois weed scientist once said herbicide pre-mixtures are a great way to “can ‘em and confuse ‘em”.

Unfortunately, fluroxypyr applied alone at 0.12 pounds active ingredient per acre (Starane Ultra at 5.5 fluid ounces per acre) only provides approximately 70 percent kochia control in hard red spring wheat over much of North Dakota. The reasons for reduced kochia control include increasing levels of resistance to fluroxypyr, product application to kochia greater than 2 inches tall, and fluroxypyr applied at a rate too low to be effective.

Dicamba-resistant kochia was first reported in North Dakota in 1995, necessitating the switch to Starane (fluroxypyr) in 1998. According to the Starane Ultra label, if dicamba-resistant kochia is present in a field, which likely occurs in most North Dakota fields, Starane Ultra should be applied at a minimum rate of 0.4 pint per acre or 0.14 pounds active ingredient per acre. 

Fluroxypyr-resistant kochia was first reported in North Dakota in 2012, yet fluroxypyr is almost never used at the rate even recommended for dicamba-resistant kochia (0.14 pounds active ingredient per acre).

Only 3 of the 31 fluroxypyr-containing pre-mixture herbicides for hard red spring wheat are likely applied at 0.14 pounds active ingredient per acre and none of these include bromoxynil to improve kochia control.

Only 4 of the 31 fluroxypyr-containing pre-mixtures include bromoxynil to improve kochia control. One of the most often used fluroxypyr-containing pre-mixtures today is Huskie FX containing fluroxypyr, bromoxynil, and pyrasulfotole. When Huskie FX is applied at the maximum rate of 18 fluid ounces per acre, it only contains 0.08 pounds active ingredient per acre of fluroxypyr, much less than the minimum recommended fluroxypyr rate of 0.14 pounds active ingredient per acre. To achieve a fluroxypyr rate of 0.14 pounds active ingredient per acre when applying Huskie FX, Starane Ultra must be added at a minimum rate of 2.6 fluid ounces per acre and kochia control MAY be completely controlled.

The new Tolvera (bromoxynil plus tolpyralate) herbicide for hard red spring wheat should be applied at 14.7 fluid ounces per acre plus Starane Ultra at least at 0.4 pints per acre for the best kochia control to less than 2-inch tall kochia.

For maximum kochia control in hard red spring wheat in 2025, apply Huskie FX, Tolvera, or Talinor at maximum rates and include at least enough Starane Ultra to achieve 0.14 pounds active ingredient. Apply when kochia is no more than two inches tall and/or before branching begins. Applying Sharpen as a soil-applied herbicide at 2 to 3 fluid ounces per acre should improve kochia control, but that may be too costly for 2025.

Neither NDSU Extension nor the NDSU Agricultural Experiment Station endorse commercial products or companies even though reference may be made to tradenames, trademarks or service names.

Always read and follow pesticide labels.

Jeff Stachler, Ph. D.
Jeff.Stachler@ndsu.edu
Extension Cropping Systems Specialist