Flea beetles are a common insect pest in early growing canola across the Prairies. There are two important species of concern for canola (and mustard) growers: the striped flea beetle and the crucifer flea beetle.
“The feeding is indistinguishable, but the striped flea beetle comes up earlier,” says James Tansey, provincial entomologist with Saskatchewan Ministry of Agriculture. In this episode of the Canola School, Tansey says that in the Saskatoon area, the striped flea beetle is already up and active, according to some reports.
Northern regions are dominated by striped flea beetles and their range is expanding, says Tansey — they like cooler, moist conditions. Crucifer flea beetles are still dominant in the southern part of the province. The different distribution has to do with their overwintering periods.
“There are some who feel that striped flea beetle can cause a little bit more damage, and there’s also some anecdotal evidence that they tend to hunker down when things are cool and wet and can feed on the stems, which can cause a fair bit of damage,” says Tansey.
For economic thresholds, 50 per cent defoliation of cotyledons and first true leaves is the point at which yield will decline. However, the action threshold, is 25 per cent, with the condition that flea beetles are still present and feeding. Tansey adds that one of the features of seed treatments that defend against flea beetles is that they’re systemic — the flea beetle has to ingest it before it will work.
When you’re scouting, make sure that it isn’t just damage you see, but also active flea beetles, says Tansey, because sometimes a high population can completely overwhelm a crop.
Populations can also be very localized, so it’s important to scout multiple areas in a field, and to look for that action threshold of 25 per cent damage to the leaves. The more plants and areas that you scout, the better idea you’ll have of what actions you need to take, and you can catch a situation before it gets out of control. Tansey also notes that flea beetles will move from the edges of fields inwards.
In the video, Tansey talks about seed treat and in-crop control options: