Rethinking Canola Trap Crops

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It’s the usual trade-off: the agricultural research community must balance promising new pest control concepts with ease of use and efficiencies for farmers.

One such concept, an integrated pest management strategy called a “trap crop,” hasn’t always been an easy sell.

The basic concept is that pests are controlled in a less valuable crop bordering the main crop and constituting 10% or less of the field. If economic thresholds are reached in the edge of the trap crop, the grower can only spray that area, avoiding the expense of spraying the entire field and potentially minimizing damage to beneficial insects in the rest of the field.

More than 15 years ago, Agriculture and Agri-Food Canada researcher Hector Carcamo published research on the use of trap crops to control cabbage seed weevil in canola.

Carcamo’s research, conducted on canola fields in southern Alberta between 2000 and 2003, found that borders planted with Brassica rapa (Polish canola) flowered a week earlier than the main crop of Brassica napus (Argentine canola ) and concentrated a very large number of cabbage seed weevils. . Sowing the same Argentine canola cultivar a week earlier than the main crop also worked, Carcamo says. By only spraying the edges of trap crops when cabbage seed weevil reached economic thresholds, the researchers realized significant savings.

It sounded good, but Carcamo says farmers were reluctant to adopt the practice. Planting two varieties in one field meant two planter passes or two planting events, and two separate harvest dates for each field later.

But the trap crops could still have their day. Carcamo has proposed new research that will revisit the concept with new burst-resistant canola varieties.

They make the difference. With older varieties, farmers had to swath during narrow harvest windows. With shatter-resistant varieties, harvest windows are wider and farmers can cut their canola straight. They could fill a seed box with the border variety, seed the border, and then switch to main crop seed for the rest of the field, Carcamo explains. At the end of the season, since they can afford to wait for both crops to mature, the two can be harvested together.

“So it doesn’t matter if you have two cultivars that have a maturity difference of five to seven days. (Farmers) harvest peas first, then barley, then wheat, and they have the luxury of leaving the canola longer – late summer or early fall. If you have a slight difference in maturity times, the two crops are catching up. »

Since canola is generally harvested after other crops, this difference would not be of concern at the end of the season.

photo:
Hector Carcamo, AAFC

Bees as pest control

Carcamo’s proposed research project includes some intriguing new approaches to pest control.

One is the use of a biological insecticide containing the fungus Beauveria bassiana, which can control immature and adult thrips, whiteflies, lygus and aphids and other insects. It is registered in Canada, but not yet for canola. He also hopes to study insect-pathogenic bacteria that could provide a similar service.

Carcamo says products like these are attractive for field crop research because they have “milder” off-target effects than conventional insecticides.

Another technology that is hoped to be tested in the field is Guelph researcher Peter Kevan’s concept of bee vector – short for “vectoring beekeeping” – which uses pollinators like bees and bumblebees to transport pest control microbes to crops. The pioneering design by Kevan and his colleagues is a distributor on the way out of the hive; the bees pass through the powder containing the spores of microbes and carry them to the flowers, where the parasites are then infected.

Carcamo says the technology has been used successfully in many greenhouse crops in Canada as well as field crops in other countries. He thinks it could work well in tandem with trap crops in canola fields, mainly because of the trap crop’s flowering time.

“I think the microbial insecticidal trap bee vector could be effective because you have a lot of canola plants blooming in early June when few other crops are blooming,” he says.

Once Carcamo’s proposal and funding come together, he hopes to assemble a team to conduct environmental impact assessments to document the benefits of climate change mitigation and biodiversity and, which is crucial for farmers, economic analyses.

Carcamo points to recent emphasis on the importance of protecting beneficial insects, in campaigns such as the Western Grains Foundation’s ‘Field Heroes’, as evidence that more and more farmers are investing in minimizing damage. pollinators and other beneficial insects.

This time around, trap crops could be a winning proposition.

Carcamo has published a useful guide on the use of trap crops researchgate.net.

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