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Old, new products deliver multi-modes of action

The challenge is to hit weeds with two or more active ingredients to reduce resistance

Old chemistry, new formulations, multiple modes of action — these are all elements farmers can include in their weed control toolbox heading into 2017, say weed researchers and crop protection specialists.

One of the most important elements these days for either preventing or managing herbicide resistance in weeds is to approach control with multiple modes of herbicide action. Some of the older chemistries used in conjunction with newer products can be very effective in reducing the risk of “selecting” weeds that have or may develop herbicide resistance, says Bob Blackshaw, weed researcher with Agriculture Canada in Lethbridge.

Products like Avadex and Edge, for example, that almost disappeared from the herbicide scene 20 years ago as farmers moved into zero till and direct seeding and relied on glyphosate and other in-crop weed control products, are finding a new fit in crop protection programs.

Goldwing, a new Group 14 pre-seeding/pre-emergence herbicide from Nufarm is a contact and system product that can be used in all cereals and fieldpeas.
photo: Lee Hart

“A few things have happened over the past 20 or so years,” says Blackshaw. “In conventional farming days there was a need to incorporate some of these products three or four inches into the soil to be closer to weed seeds. With direct seeding systems we are finding more of the weed seeds in the top inch of soil, so they are closer to the surface. Incorporating a herbicide isn’t necessary.”

And while some of the older products such as Edge and Avadex have the same name, new formulations have made granules smaller and more concentrated so they are more effective, even without incorporation. They still need moisture to carry them into the soil, but again conservation-farming practices help to retain more moisture at or near the soil surface.

Blackshaw says it is important to use pre-seeding products in conjunction with in-crop treatments to achieve different modes of action. The pre-seeding herbicide product with one mode of action delivers the first punch on weeds. Depending on the product it may control 70 to 85 to 90 per cent of weeds, while in-crop treatments with different modes of action deliver the second or third or knockout punch, depending on the tank mix. “Even if your pre-seeding product is only 70 per cent effective, that’s still a considerable reduction in weed numbers,” says Blackshaw. “And then with effective in-crop treatments you can clean up the rest.”

Take a look at Group 14

While older products such as Avadex (Group 8) and Edge (Group 3) have a fit, Nufarm has several new and newer products delivering different modes of action to help with early season weed control, says Graham Collier, Nufarm technical service manager for Western Canada.

These Nufarm products are all based on Group 14 chemistry (described as PPO inhibitors) providing effective pre-seeding weed control in various crops covering a broad spectrum of weeds.

“Research has shown over the years repeated use of certain active ingredients have increased herbicide resistance in weeds,” says Collier. Pointing to work done by Hugh Beckie, Agriculture Canada researcher, the risk of Group 2 herbicide resistance is one in 100,000 plants, while the risk of Group 1 resistance is one in one million plants. But then once you start to add multiple modes of action the risk decreases substantially. If you’re using Group 4 and Group 9 chemistries, for example, they each have a one in 100 million risk of an individual weed having natural resistance to a chemical. And if you combine, tank mix, the two products the risk decreases to one in 10,000,000,000,000,000.

And when you throw a Group 14 product into the tank mix the risk really diminishes. Collier says a tank mix that includes Group 4, 14 and 9 chemistries reduces the herbicide resistance factor to one in one septillion. (If you want to see what a septillion looks like, it is the number 10 with 23 zeros after it.)

So what pre-seeding products are in the Nufarm lineup?

  • Conquer isn’t brand new and is largely an upgrade to an earlier Nufarm product, CleanStart. Conquer is a pre-seeding product that can be used ahead of canola. It is a combination Group 14 and 6, herbicide (carfentrazone and bromoxynil) and can be tank mixed with glyphosate. It can be very effective in controlling both smaller and larger volunteer glyphosate-resistant canola.
  • Valtera is another Group 14 herbicide (flumioxazin) that can be tank mixed with glyphosate. A residual herbicide, it can be either spring or fall applied. As a pre-seeding treatment it can be used ahead of peas, spring wheat, chickpeas and soybeans and further registrations are expected.
  • Goldwing is a brand new Western Canada developed product from Nufarm — also in Group 14 with a Group 4 (pyraflufen-ethyl/MCPA (ester). A contact and systemic herbicide, it can be tanked mixed with glyphosate and used pre-seeding or prior to emergence, ahead of all cereals, field peas and corn, and again future registrations are expected.
  • Blackhawk is another new combination Group 14 and Group 4 contact and systemic herbicide (pyraflufen-ethyl/2,4-D ester) that can be tank mixed with glyphosate. It can be applied prior to seeding or pre-emergence and can be used with all cereal crops and soybeans. It can also be used in summer fallow and post-harvest applications.

All four of these products have a wide spectrum of weed control with details available on the Nufarm website.

Range of pre-seeding products

Producers have many familiar pre-seeding products to consider.

  • Edge is a Group 3 (ethalfluralin) selective pre-seeding granular herbicide providing weed control in oilseed and pulse crops. It’s marketed by Dow AgroScience.
  • Avadex MicroActiv Herbicide, is a Group 8 (triallate) granular herbicide that can be used spring or fall in conventional and direct seeding systems. It provides wildoat control in spring and durum wheat, barley, canola, most flax varieties, yellow, brown and oriental mustard, sugar beets and canary seed. Avadex is marketed by Gowan Canada.
  • Aim EC is a Group 14, PPO inhibitor (carfentrazone) that can be tank mixed with glyphosate, providing pre-seed weed control ahead of canola, pulses and cereals. Marketed by FMC — Canada.
  • Authority is a Group 14, PPO inhibitor (sulfentrazone), that can be used as a pre-seeding/pre-emergence herbicide. It provides residual action in the soil and can be used ahead of crops such as field peas, flax, faba beans, chickpeas, sunflowers and soybeans. It can be tank mixed with glyphosate. Marked by FMC Canada.
  • Heat is a Group 14 chemistry (salflufenacil) developed by BASF for pre-seed, pre-emergent and chemfallow applications. It can be tank mixed with glyphosate and applied ahead of cereals and pulse crops. It also works as a harvest aid to desiccate crops.

Valtera is a Group 14 residual spring and fall herbicide that can be used with peas, spring wheat, chickpeas and soybeans.
photo: Lee Hart

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Field Editor

Lee Hart

Lee Hart is editor of Cattleman’s Corner based in Calgary.

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