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Avadex back in the game to fight herbicide resistant weeds

When herbicide resistant wild oats crop up on you’re farm, you may be looking backwards in time to find a solution with a different, “new” active ingredient

The Brady Bunch. ABBA cassettes. Avadex. Things we remember fondly, but don’t really see much anymore. Right?

Wrong. Avadex is back in town.

In 2004, Gowan, an Arizona-based company, bought the formulation and trademarks from Monsanto. As wild oats with resistance to Group 1 and Group 2 herbicides continue to pop up across the Prairies, farmers are searching out new (or in this case, old) ways to control these resistant weeds. Farmers who don’t yet have herbicide resistant weeds are looking for different modes of action to add to their herbicide rotations, in hopes of slowing the speed of resistance development. Adding a Group 8 soil residual herbicide to the rotation can meet these needs.

Avadex and Fortress bring different chemistries back to the field. At a meeting of herbicide retailers in Saskatoon, Gowan Canada’s Javan Davis talked about the benefits of going back to Avadex. “We’re not going after every acre,” Davis said. “We’re going to go ahead and try to get growers to start using the product. A lot of young guys are just starting, and even though it’s a 50-year old product, it’s new to them.”

To make sure retailers and agronomists are up to the challenge of helping farmers go back to Avadex, Gowan convened a meeting in Regina to cover the basics.

The products

Davis was talking about three different herbicide formats: Avadex as a liquid, Avadex as a granular, and Fortress, a granular. “We are in the process of moving Fortress into a microactive granular also, so a little bit of a smaller granule, to make it a little more efficient — a little easier to use,” Davis said.

Avadex is a Group 8 soil-applied, pre-emergence herbicide. Its active ingredient is triallate. Fortress is a Group 8 and 3 soil-applied, pre-emergence herbicide, with triallate and triflurlalin as active ingredients.

“Where we’re seeing the best control of wild oats is fall applied granulars,” Davis said. “Granulars applied in the fall are out-preforming spring-applied granulars or liquid.”

Gowan recommends that farmers, “ensure maximum soil contact and incorporate to build a herbicide barrier in the top one to two inches of soil for best control of wild oats.”

Davis said farmers applying granulars in the fall are getting 85 to 90 per cent control of wild oats, “where in the spring we’re seeing 80 to 85 per cent control.” In the best cases, farmers are harrowing the product in the fall, then leaving it on the field until they do a pre-seed burndown.

While the product needs to be worked in, Davis stressed that they’re not talking about harrowing, not cultivating. “We’re trying to get away from traditional tillage thinking.”

Davis says the possibility of applying a granular herbicide in the fall gives farmers more options. “With the last couple of years its been wet in the spring so you haven’t been able to get out there.”

Tips for users

Davis was careful to remind retailers to make sure farmers know that Gowan does not offer a warranty on Avadex and Fortress. “We can’t guarantee control, depending on different field conditions,” Davis said.

There are many factors to consider when using granular herbicides. Gowan is expanding its rep network to help farmers use the products correctly. “We want to service the product before it goes out the door.”

The biggest decision farmers need to make is whether to use Avadex in liquid or granular form. Davis recommends that farmers consult with their sales rep or agronomist before they decide, perhaps even emailing a photo of the field so your rep can take a look at the trash on the ground. Contact with the soil is very important — trash on the ground can tie up the products’ active ingredients.

Gowan recommends: “For early fall applications, simply apply granular Avadex or Fortress, heavy harrow and plant the following spring. For later applications, apply before snow cover and then make another harrow pass and plant in the spring.”

Making sure that granules contact the soil may require a little advance planning. For example, having the combine chop the straw more finely. Some farmers might harrow ahead of time, blow on the Avadex or Fortress, then harrow again.

Here are some other suggestions Davis asked retailers to pass on to their customers.

  • If you’re using Avadex on a field that will be seeded to cereal crops, you need to “make sure your cereal crops are seeded below that treated layer,” Davis said. “You don’t want those cereals germinating in the treated layer, or you’re going to end up with some crop injury.”
  • Make sure the soil temperature is below 5 C when you apply granulars in the fall. While daytime may go above 5 C, Davis said, “when the majority of the temperature is under 5 C, you’re okay to go ahead and apply it.”
  • In the spring, once the soil temperature is above 5 C, the product will begin to activate. Granulars will take 10 to 14 days to activate. Liquid Avadex will activate right away. If you’re not doing a pre-seed burndown, if you apply the granular, and then seed four or five days later, and some of those wild oats are germinating, you’re “going to have a lot of escapes,” Davis said.
  • Some farmers are finding better results by harrowing with the rows — if your harrows are plugged, they’ll drag the granules around the field. “What you’re trying to do is get your granules in contact with the soil.”
  • Because the product needs to contact the soil, Davis said, “Large clods and lumps are the enemy.” You may need to harrow to break up dirt lumps to prevent escapes.
  • If you’ve burnt your fields, do not apply Avadex for at least a year. The carbon residue left after the burning will tie up the active ingredient. “Even if it’s harrowed,” Davis said, “there’s still enough charcoal left in the field to tie up that triallate.
  • Gowan says: “Minimum tillage canola fields can be fall treated with Avadex or Fortress. The granular formulations will readily penetrate relatively thick trash. Apply the granules in the fall, harrow aggressively and plant in the spring.”
  • With this year’s late harvest, Davis said farmers have been asking if they’ll be able to apply Avadex on frozen ground. “As long as they’re going to get that soil contact sometime before seeding,” it will be alright. “If there’s a skiff of snow don’t be afraid of going ahead and throwing it in.”

Davis suggests that farmers who haven’t used Avadex before start out on a small scale, perhaps using Avadex (or Fortress) on 10 to 20 per cent of their fields each year. Adding a different mode of action to crop protection plans can help prevent wild oats from developing resistance, or at least lengthen the time it will take for resistance to develop. “I have a few 20,000, 30,000 acre guys that are doing one third of their farm every year,” Davis said. “That’s going to be their program. They have Group 1 resistance, they’ve identified it, so that’s what they’re going to be doing.”

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