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The future of weed control

While high costs are still a hurdle to overcome, bioherbicides are in the works and could be a weapon in the struggle against herbicide resistance

While high costs are still a hurdle to overcome, bioherbicides are in the works and could be a weapon in the struggle against herbicide resistance.

Researchers in Canada and the United States are developing bioherbicides that will not only give organic and conventional farmers more weed control options, but also, in some cases, control herbicide-resistant weeds.

Bioherbicides are synthetically produced compounds identical to chemicals found in nature. They may be sourced from micro-organisms or plants. Bioherbicides can also include whole microorganisms that infect weeds.

Currently there are no bioherbicides registered for use on agricultural crops in Canada, but researchers with Agriculture and Agri-Food Canada (AAFC) are working to change that.

Fungal bioherbicides

Phoma is a fungal bioherbicide that controls Canada thistle, dandelion and wild mustard. Health Canada’s Pest Management Regulatory Agency (PMRA) approved Phoma for turfgrass in 2011, and it will be commercially launched in 2014.

Dr. Karen Bailey is an AAFC researcher based in Saskatoon. Bailey and her colleagues are studying the use of Phoma in agricultural crops and she plans to study Phoma’s efficacy in wheat and barley this year. She already has two years of data on alfalfa, funded by the alfalfa seed commissions in Saskatchewan and Alberta.

Wide row spacing leaves alfalfa crops vulnerable to weeds before the crop is established. So far Bailey’s results are positive, though she has found using Phoma the year the alfalfa is seeded harms the crop.

“And the interesting part that we found actually with the alfalfa was that even though it harmed the crop in the first year, by the time it had its next year, the crop had recovered so that there were no differences among our treatments relative to an untreated control,” says Bailey. Applying Phoma in the years after the alfalfa is seeded doesn’t harm the crop.

Bailey says organic farmers are very interested in using Phoma to control weeds such as Canada thistle. She thinks some conventional farmers may use it as well.

“I think it’s going to be probably (a fit with) some people’s philosophies, as long as the product works. And I think some people will find it as an alternative to be able to use in some situations. In other cases it may just be a novel way of control for them.”

Whether Phoma proves useful for treating herbicide-resistant weeds depends on which weeds it’s approved to treat, Bailey says.

“But we do know bioherbicides do provide different mechanisms of action.”

Bailey’s colleague, Dr. Susan Boyetchko, is studying bacteria that control wild oats and foxtail. Boyetchko’s work shows that bacteria control herbicide-resistant weeds.

Bioherbicides in the U.S.

There aren’t many bioherbicides on the market in the United States right now, either, and many are aimed at the organic market.

Marrone Bio Innovations is a California company that develops biopesticides. The company’s bioherbicide, Opportune, has been approved by the U.S. Environmental Protection Agency (EPA). Marrone Bio Innovations has also submitted Opportune to the PMRA for approval in Canada.

“Historically bioherbicides have not broken through and (have had) very small sales because somebody would look for a microbe that would infect and kill a weed,” says Dr. Pam Marrone, CEO of Marrone Bio Innovations.

Part of the reason previous efforts have had limited success is that the microbes being used only worked on a few specific weeds. Bioherbicides that control more weeds have more potential for conventional agriculture, especially with growing herbicide resistance.

The active ingredient in Opportune is a microbial compound, rather than the entire microbe.

“There’s no infection process of the weed. It’s strictly based on the microbe producing a compound. The compound kills the weed,” says Marronne.

The compound is selective, so it won’t kill grasses such as corn, wheat, rye and turf. Marrone says it controls broadleaf weeds in grasses post-emergence, and can be used in any crop before planting.

Marrone Bio Innovations also has two bioherbicides on deck. One, which has been submitted to the EPA, uses a compound from a Chinese pepper plant, and can be used as a post-emergent burndown for grasses and broadleaves. The other bioherbicide uses several compounds from a bacterium.

Lowering costs a priority

“The problem with (chemical) herbicides is that they’re so low-priced that it’s hard to find bioherbicide technology that can get you down to the price to compete,” says Marrone.

When researchers and companies first find a bacterium, plant, fungus, or other organism that produces the compounds they need, Marrone says one of the first goals is to increase the source’s yield while lowering costs.

“When you first launch the product, you’re going to have a higher cost of fermentation. And so over time, you’ll be improving the yields and getting the cost down. So our first initial entry point will be the organic market,” says Marrone.

Over time, Marrone says they’ll be moving into the conventional market. Marrone Bio Innovations is developing several active ingredients that they plan to mix and match, similar to regular tank mixes. But that doesn’t mean traditional chemical herbicides will be obsolete.

“Our active ingredients synergize. So they make the chemical pesticides better.”

Marrone says Opportune controls glyphosate-resistant weeds. She sees Opportune as a way to spike chemicals, such as glyphosate, to make them more effective.

Weeds aren’t likely to develop resistance to bioherbicides because they have complex modes of action, says Marrone. Resistance is possible, but still unlikely, with bioherbicides that rely on a single compound, she adds.

“On the biological front, the success to date has been in high-value crops and in insecticides and fungicides. And I think the next wave will be in the herbicide area because of the resistance development,” says Marrone.

— Lisa Guenther is a field editor with Grainews based at Livelong, Sask. Contact her at [email protected]

Biologicals in Canada

Though Canadian farmers can’t pick up bioherbicides yet, they’re already using other biological products.

Inoculants contain rhizobia, live bacteria that help plants take up nutrients such as phosphate and nitrate. Biological insecticides are also available. For example, Novozymes markets an insecticide that uses fungal spores to control insects in the greenhouse and nursery industries. — L.G.


About the author

Field Editor

Lisa Guenther

Lisa Guenther is field editor for Grainews based at Livelong, Sask. You can follow her on Twitter @LtoG.



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