26 March 1999

Biological weapons are deployed in the war against weeds

CANADIAN scientists are busy setting natural soil bacteria to work against common weeds, with growing success.

When a Canadian prairie farmer reports finding an unusual barren patch in a field, more often than not researchers from Agriculture Canadas Ecological Crop Protection group in Saskatoon visit to collect samples for analysis.

"A handful of soil contains millions of bacteria," says Ag Canada research scientist Susan Boyetchko. If something is affecting tough weeds like wild oats she wants to identify the bacteria and help it proliferate.

The bacterial soups simmering inside Agriculture Canadas Saskatoon laboratory may be the next wave in crop protection products, helping solve herbicide-resistant weed headaches and cut pesticide use, says Ms Boyetchko.

The Canadian prairies face a growing problem of herbicide resistance. Northwest Manitoba, for example, has wild oats resistant to four herbicide groups, including some that have never been used there.

As a result, the 20-member research team is focused on isolating and cultivating bacteria and fungal agents to control wild oats and another herbicide-resistant weed, green foxtail.

Researchers are evaluating more than 200 bacterial strains, reports Ms Boyetchko. Once one is shown to suppress a particular weed species consistently, researchers set out to determine how it works as well as the temperature and moisture conditions that will keep it alive and active.

The next, and perhaps most challenging step, is developing a delivery mechanism for on-farm use, either as a foliar spray or in a granular formulation.

Three bacterial strains show good promise, one of them targeted for wild oat control and two for green foxtail. A two-year field test on green foxtail gave 50% control with one strain.

Some of the bioherbicides already available in North America include Canadas first registered bioherbicide for control of round leaf mallow, a fungal foliar pathogen applied as a wettable powder for weed control in rice and soybeans and a soil fungus for control of strangling vines in citrus orchards.

Developing biocontrol organisms does not necessarily involve genetic modification, Ms Boyetchko says. But researchers do routinely insert genetic markers so they can be identified in the field.

So far the agrochemical industry has not been interested in funding much research, says Ms Boyetchko. But some small companies are interested.

One such is Saskatoons Micro-Bio RhizoGen Corp. Its first products are a granular rhizobium inoculant for legumes and a delivery system for bioherbicides and other soil-borne agents. &#42

BIOHERBICIDES

&#8226 Based on soil bacteria.

&#8226 Selected in lab.

&#8226 Useful strains found.

&#8226 Application challenges.

&#8226 Products already commercially available in North America.