Herbicide “layering” strategy delivers multiple punches

Effective for weed control and reduces risk of herbicide resistant weeds surviving

Corey Loessin has for several years been delivering the one/two and sometimes multiple punches through the pulse crop weed control program on his northwest Saskatchewan farm.

Primarily growing red lentils and yellow peas near Radisson, northwest of Saskatoon, Loessin says his main objective is to use different products with varying modes of action to control weeds while minimizing the use of Group 2 herbicides.

“I think I was layering herbicides long before it was actually called layering,” says Loessin who also includes cereals and canola in rotation. “Some of the Group 2 products are still useful, but there is just an awful lot of herbicide resistance involving the Group 2 products so we need to be doing different things.”

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Loessin, who aims to grow about 1,000 acres of pulses crops each year (divided between peas and lentils) follows a slightly different weed control program with each of the pulse crops. Peas may be a bit more competitive against some weeds than lentils, so he treats the two crops differently.

The yellow pea program

The first step in the weed control program on fields to be seeded to yellow peas, involves either a fall or early spring broadcast application of granular Edge, a Group 3 product from Gowan.

“With the peas I use it more as a spot treatment,” says Loessin. “I broadcast apply with a Valmar spreader and heavy harrow and really just treat those areas where kochia or wild oats might be a particular problem.” At $20 per acre for Edge, he says he tries to reduce costs with the spot treatment, knowing the peas can handle some weed competition.

The next treatment on pea fields is a pre-seeding burn off with glyphosate, Group 9, tank mixed with Heat, a Group 14 product from BASF. That’s followed in-crop with Viper, also from BASF, which is a combination of both Group 2 and Group 6 chemistries.

“Probably the Group 2 component isn’t of much value if you have kochia with resistance to Group 2,” says Loessin. But then it also has the Group 6 component, which does provide effective control.

The lentil strategy

While in a reasonable growing season red lentils can be quite productive and profitable, Loessin says they aren’t very competitive with weeds, including volunteer cereals, so he pays particular attention to keeping fields clean.

In lentil fields, weed control starts with a fall application of granular Edge (again a Group 3), broadcast applied with the Valmar spreader and heavy harrow. Edge is only registered for a fall application ahead of lentils. “And I treat the whole field, not just a spot treatment,” says Loessin. “Lentils just aren’t competitive at all so it is worthwhile to do the whole field.”

In the spring that is followed either by a pre-seeding or a pre-emergent burnoff with either straight glyphosate or glyphosate tank mixed with Heat. “Depending on the year and the field, I prefer to use it as a pre-emergent,” says Loessin. “About a week after seeding, I’ll apply the burnoff products, giving weeds another week to emerge. It can be riskier, but if we pay attention to our timing, it also can provide more effective weed control.”

In-crop with Clearfield lentils, Loessin applies either Solo, Group 2, BASF, or ARES, Group 2 now owned by Corteva. “They are both Group 2 products but ARES is particularly effective on cleavers and also has residual activity,” says Loessin.

According to product information one year after an application of ARES, follow-crops can include canary seed, chickpeas, field peas, field corn Clearfield canola, Clearfield juncea, spring wheat — including Clearfield spring wheat, spring barley, and tame oats. Durum wheat can be grown after two years.

Another weed Loessin has to really watch for in red lentils is volunteer wheat. “It is almost impossible to clean wheat out of red lentils so really there is zero tolerance,” he says. “If I see volunteer wheat I may need to go in and spot spray with something like Centurion, Group 1, to control the cereals.”

Post-harvest limitations

Loessin says while there are several weed control options while pulse crops are growing, producers are limited to the products they can use pre-harvest, particularly with lentils, to get them stopped.

“With some products the maximum residue levels (MRLs) have not been established, so buyers don’t want crops that have been treated with these pre-harvest products,” he says. “And with lentils in particular, you need something to desiccate the crop and stop it from growing. And Reglone is about the only option.” Loessin says he has done on-farm trials with pre-harvest products and left check strips of untreated lentils. “And they just keep growing,” he says. “They stay green with no sign of dying down naturally.”

Loessin says with more pulse crop acres, and Reglone as the only option for a desiccant it is cause for concern. “I don’t think we should be relying on just a single product in any aspect of crop production,” he says. “So for pre-harvest products, more work needs to be done to develop products or have more products cleared for use.”

BASF recommendations

And at BASF, Dan Packer, senior herbicide brand manager, says the company has produced simple recommendations of herbicide products that can be used in combination or in sequence as part of its Advanced Weed Control Program for pulse crops, soybeans and corn. The strategy known as herbicide layering involves applying multiple herbicide modes of action and groups in sequential application.

“For these crops in particular we have developed recommendations for pre-seed products as well as in-crop products for the various crops,” says Packer. “Perhaps each on its own may not provide effective control of all weeds, but when used in combination they are very effective.”

For field peas and glyphosate-tolerant soybeans, for example, BASF recommends the same program for both crops. It starts with a pre-seed burnoff with Heat LQ, a Group 14 or for broader weed control Heat Complete, which is a combination of Group 14 and 15 herbicides that will provide control of Group 1, 2 and 9 herbicide resistant weeds. The Heat products are followed in-crop with Viper ADV, which is a combination of Group 2 and 6 herbicides.

For Clearfield lentils, the recommendation is to use Heat Complete, Groups 14 and 15 for the pre-seed burnoff, followed by Odyssey Ultra NXT, or Solo Ultra, both Group 2 products for use in-crop.

For dicamba-tolerant soybeans, the pre-seed recommendation is to use Engenia, Group 4 herbicide in combination with Heat LQ or skip those two and go with Heat Complete, the Group 14 and 15 combo. The pre-seed treatment should be followed by Viper ADV in-crop.

And for corn growers, start out with a pre-seed treatment of either Heat LQ or Heat Complete, followed by Armezon, a Group 27 herbicide in-crop.

More details on these recommendations can be found on the BASF website. On that page, look for the Advanced Weed Control Program.

About the author

Field Editor

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

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