Friend or Foe? Identifying what’s what when you sweep

June 24, 2019

As seeding, for the most part, has come and gone — it’s now time to scout!

In this episode of the RealAgriculture Canola School, field editor Jessika Guse speaks with Dr. Meghan Vankosky, research scientist in field crop entomology with Agriculture and Agri-food Canada, all about what to look for when you sweep.

Her first recommendation is to know how to properly sweep when you get out in the field as some will sweep too short, and others might sweep too long.

“This time of year it’s important to start scouting for those insect pests that you might expect in your crop by commodity,” Vankosky says, adding it’s good practise to begin looking at the Prairie Pest Monitoring Network blog (PPMN), to get a heads up on what you’re looking for.

When you do get out in the field, it’s important to use a standardized sweep net that has a 35” long handle and 15” (38 cm) diameter net, as that’s what most economic thresholds are based off of.

“When you go out and sweep, you’re going to take nice 180-degree sweeps in front of you as you’re walking,” she says. “If you want to open the net up, and look right away in the field, you are going to have things fly out of the net, at you right away, those are often the beneficials or the good things like the pollinators or the natural enemies.”

To get a good grasp of what’s in your field, after you sweep, twist the net to keep the insects inside and take them straight to the fridge.

“Often the bad things, or the foes or pests, are what you’re going to find deeper into the net,” she says.

A few foes that you don’t want to find in your canola field, but likely will:

  • Bertha army worms
  • Striped flea beetle
  • Crucifer flea beetle
  • Cabbage seed pod weevil
  • Lygus Bugs

As far as beneficials go for canola, the “good guys” include:

  • Green lacewings
  • Rove beetles
  • Lady beetles (also called ladybugs)
  • Parasitoids
  • Bees

Depending on what you have in your net, will depend on the next mode of action you take for your crop. For a list of free guides of economic thresholds per insect from the PPMN, click here.

(Although this is a Canola School the dry conditions had held back the canola crop, so we had to sweep an alfalfa field. Adjust and overcome, y’all)


Canola School videos are produced by Real Agriculture.

You can watch all the canola school videos on this website and on Real Agriculture's Canola School page

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