Not seeing flea beetles? Doesn’t mean they aren’t there

May 29, 2019

Across the Western Prairies, flea beetles are starting to pop up in canola crops.

As your canola crop moves from the cotyledon stage to the first true leaf stage, you want to ensure you are keeping an eye on potential feeding.

In this episode of Real Agriculture’s Canola School, Kara Oosterhuis talks to Autumn Barnes, agronomy specialist with the Canola Council of Canada, about scouting flea beetle damage, and the economic thresholds that warrant action.

“It’s really important when we are scouting for flea beetles, and we are assessing the damage, that we don’t use the presence or absence of the beetle itself as a way to decide if we’re in trouble or not,” explains Barnes. “What we’re looking for is the damage, and if that little canola plant is growing actively, and is going to be able to grow past that damage.”

“Not seeing them doesn’t necessarily mean we aren’t going to spray. Those little guys can be difficult to find at times.”

Barnes compares the damage on the cotyledons to look something similar to a divot in a golf-ball. “Usually it looks like a little pockmark. They take little bites — because they are tiny, little beetles — and if there is a lot of them feeding really voraciously then the pockmarks will get big. Sometimes the marks will kind of dry out and turn brown, but if they are fresh bites, they will sometimes be a bit of a dark green.”

She also notes that the Canola Council has an action threshold of 25 per cent on flea beetle damage, and an economic threshold of 50 per cent.

“At 25 per cent we’re not seeing a yield penalty for that flea beetle feeding. But when you get up to that 50 per cent leaf area loss, that’s when the cost of the spray is getting paid for by your application… At 25 per cent you should probably be lining up where you are going to get your chemical from, when you’re going to spray, figure out your logistics.”

In flea beetle favourable conditions, Barnes cautions that damage can jump from 25 to 50 per cent in just one or two days.


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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