insects Flea beetles may be more evident this yearas a dry August forces them higher into the canopy
Some Manitoba farmers have been spraying for flea beetles a little later than they’re used to, but experts say this year’s jump in late-summer flea beetle sightings shouldn’t automatically sound the alarm.
“Canola can handle a fair amount of flea beetles late in the season,” according to an Aug. 19 crop pest report from the province, “particularly if the crop is in the green stage or beyond.”
Pod damage due to late flea beetle feeding has been a concern in eastern Manitoba and a few producers have sprayed for the pests, according to the Aug. 25 provincial crop report.
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The province also reported high flea beetle numbers in the Interlake.
There has been some spraying for late flea beetles, but much like leaf damage in the spring, producers want to make sure they have actually reached an economic threshold before looking at control.
“The flea beetles have always been feeding at this time of year,” said Justine Cornelsen, agronomy specialist with the Canola Council of Canada.
However, hot and dry weather in August may be making the insects more visible this year, she noted. Lower leaves are drying out, pushing the pests higher into the canola canopy where they’re easier to notice.
While they sometimes do penetrate the pod and compromise seed, the insects mainly eat leaf material, and when they do eat pods they usually strip the outer material without breaking into the pod itself, according to Cornelsen.
“They’re not wiping out entire fields,” she said.
The pests will move to headlands or grassy areas to overwinter. However, there’s no direct correlation between the late-season population and what emerges in spring. You can’t predict what winterkill will do, Cornelsen said.
The province advised keeping an eye on how much pod damage is occurring, and to control the flea beetles if they appear to be an economic threat to this year’s canola.
“If not, the most economical decision is to avoid the late-season insecticide application and deal with levels that may emerge in the spring,” the provincial pest report said.
Provincial entomologist John Gavloski also reminded farmers that, once a crop is within seven days of swathing or straight combining, it can’t be sprayed.
