Posted: July 14, 2009

Once available, fungus-based selective broadleaf herbicide may be a supplement to chemical pesticide use in agriculture

Researchers are in the final stages of the development of a selective broadleaf herbicide that uses an indigenous fungus as its active ingredient. However, the lead researcher on the project warns producers not to cancel their chemical pesticide orders quite yet.

Agriculture and Agri-Food Canada (AAFC) in Saskatoon, Saskatchewan are kicking off research efforts to discover applications for Phoma macrostoma in agriculture, says research scientist Karen Bailey, who first isolated the organism in 1996.

Preliminary studies have shown that the fungus can provide effective weed control when applied to cereal or grass seed production systems. The next steps, says Bailey, are to test the overall feasibility of the product for agricultural use and find an industry partner with agricultural experience. "For turfgrass applications, the product should be available in a few years as it takes 14 to 18 months for regulatory assessment," she says. "It is likely five years away from being available for agriculture."

Regardless of how feasibility testing and regulatory assessment pan out for the product, however, Bailey warns that bioherbicides will likely not offer a one-size-fits-all solution for an industry fighting negative consumer perception of its dependence on chemical pesticides.

"In agriculture, producers will still need pesticides," she says. "Bioherbicides provide another tool that should be used as part of an integrated pest management strategy. Once we have a few bioherbicides available in agriculture then we can demonstrate how this may be successfully done. However, bioherbicides will not replace herbicides. Bioherbicides may fill some specific niche markets, such as being used by the organic industry or in situations where herbicide resistance has developed."

What it is, where it's at

Phoma macrostoma is an indigenous fungus isolated from naturally-infected Canada thistle plants. Research has found that it has limited mobility in soil and requires moderate temperatures and light to moderate moisture content to be effective. "It is not very competitive and its presence declines with time. One year after application, it is rarely detected in the soil and there are no carryover effects to subsequent crops," says Bailey.

"We have completed the toxicological and environmental risk studies and are preparing a submission to the Pest Management Regulatory Agency in Canada and the Environmental Protection Agency in the U.S. to register the bioherbicide for use in turf. Since 2003, AAFC has been working under a collaborative research and development agreement with The Scotts Company and Scotts Canada, who will be submitting the product for registration."

There is still much work to be done to determine how the product works in a crop setting, says Bailey. "We need to learn the range of agricultural weeds that can be effectively controlled, look at the formulation and application methods suitable for agriculture and likely modify these for larger scale application, test our agricultural parameters in field studies over a few years and environments, determine the economic feasibility for agricultural use, and complete additional toxicological tests required for the registration of a bioherbicide that would be applied to food and feed crops."

More information on Phoma macrostoma can be found in this fact sheet.