Guenther: Late-season flea beetles are next spring’s problem

Flea beetle. (CanolaCouncil.org)

The growing season is winding down, but pest insects are still feeding in parts of the Prairies. Here’s an overview of what farmers, agronomists and entomologists are seeing in the fields — and what farmers can do about it.

Late season flea beetles showing up

Scott Meers and Shelley Barkley of Alberta Agriculture and Rural Development (AARD) hosted an insect chat on Twitter Wednesday morning. Flea beetles were on the agenda.

Jason Casselman, an agronomist with Dunvegan Ag Solutions in the Peace area, tweeted that he’d noticed striped flea beetles while checking for lygus bugs. Meers reported that the flea beetles he’d seen in the south were mostly crucifer flea beetles. Meers also noticed striped flea beetles in central Alberta while checking for bertha armyworm.

Late season flea beetles feed and then hibernate as adults through the winter, Meers wrote. “The flea beetles we are seeing now will be the ones that attack seedling canola next year.”

The latest issue of Canola Watch noted late flea beetle numbers are higher than the Canola Council has seen in years, which could mean higher numbers next spring.

But canola growers shouldn’t spray for late-season flea beetles unless beetles are eating pods over a wide area. There is no official threshold for flea beetles, but the Council notes the numbers may have to be as high as 100 per plant before it’s economical to control them.

Manitoba Agriculture, Food and Rural Initiatives doesn’t recommend spraying flea beetles in the hopes of controlling next year’s populations, as the flea beetles can move in from other areas. The ministry also notes there can be big differences between spring and fall populations.

Grasshoppers plague parts of Prairies

The last crop report from Alberta Agriculture noted grasshopper populations are moderate to severe in parts of the Peace. Casselman reported that Alberta Agriculture’s forecast map was accurate, with the exception of a couple hotspots in the Fairview area that weren’t forecasted.

Farmers in southwestern Manitoba saw grasshoppers as well. Grasshoppers were also reported in central Manitoba, but their numbers are declining, according to the latest crop report.

Grasshoppers are also munching through crops in southern, east-central, and northwestern Saskatchewan, according to Saskatchewan Agriculture’s latest crop report.

Manitoba farmers and agronomists interested in reporting grasshopper populations can report their results to John Gavloski, entomologist with MAFRI. Details on grasshopper reporting are available online. Sites should be surveyed by the end of this month, and numbers reported by the end of September.

A wet fall will dampen grasshopper egg laying to some extent, Meers wrote, while a long, open fall will encourage egg laying. Alberta Agriculture staff members are now compiling grasshopper survey results, which are conducted by ag fieldmen in each county. The grasshopper forecast will be available in January.

Bertha marches through canola

As canola crops dry down and are harvested, hungry bertha armyworms may move on to greener fields. This could put late canola fields at risk, the Canola Council of Canada notes.

But farmers shouldn’t automatically spray, even if their neighbours’ fields have reached thresholds. Bertha armyworm numbers can vary within a small area. The Canola Council has tips on scouting and economic thresholds online.

Bertha armyworms are damaging some crops, according to Saskatchewan Agriculture’s last crop report. Some farmers in east central and northeastern Saskatchewan are spraying for the worms. Localized bertha armyworm populations were also reported in the southeast, and the pests are causing some crop stress in west-central Saskatchewan. There are also some bertha armyworms in southwestern Manitoba.

Wheat midge in Peace

Meers has been hearing reports of wheat midge from the central Peace. AARD staff are about to begin soil sampling for next year’s wheat midge forecasts, and they are looking for fields to sample.

“If a farmer co-operates with us, we will email him results from his field once I have finished processing the samples,” Barkley wrote.

A small parasitic wasp often checks wheat midge populations. Meers and Barkley can evaluate the level of parasitism in a given field.

Spraying is not recommended once the wheat crop has reached an advanced stage of flowering.

Lygus in Sask. and Peace

Lygus bugs are showing up in canola fields in northwestern Saskatchewan and in the Peace region.

The Canola Council explains that as canola pods mature, lygus bugs will move on to side branches with less mature pods. Farmers still seeing lygus bugs should see how much yield rests in the less mature pods and consider whether or not there’s enough moisture to fill the developing pods. Farmers should also check pre-harvest intervals before spraying.

Aphids near Lavoy

Terry James, a farmer based near Lavoy, Alberta, wrote he’d seen quite a few aphids.

Meers explained that aphids usually form colonies on individual canola stems, which causes deformed growth. The threshold for aphids in canola is very high, Meers added.

An AARD factsheet suggests looking for aphid clusters at the end of shoots. If farmers count 25 aphids per 10 cm on the shoots, the threshold may be breached.

From September onward, Meers and Barkley will be holding #ABbugchat the second Wednesday of every month. The next chat is slated for Sept. 11 at 10 a.m. MT.

— Lisa Guenther is a field editor for Grainews at Livelong, Sask. Follow her on Twitter @LtoG.

About the author

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Field Editor

Lisa Guenther

Lisa Guenther is field editor for Grainews based at Livelong, Sask. You can follow her on Twitter @LtoG.

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