Bring out your dead (bugs)

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Traps stand watch for tree pests

Kevin Veenstra pokes about a field of corpses using a twist-tie.

It’s a smoky Thursday afternoon, and the city arborist is checking one of St. Albert’s many insect-monitoring traps.

This one is a glue-covered square of paper about the size of his chest that was wired to a lamppost near the Willoughby Clubhouse. After almost a month, it’s become a graveyard for hundreds of aphids, ladybugs, and flies (one of which is still twitching), as well as one red crane fly. A long-legged black ichneumon wasp with a wicked ovipositor lands next to it. Veenstra nudges it free from its sticky doom.

“If you’re an entomologist, you can actually find a trove of information in this,” he says of the traps.

But from a pest-monitoring perspective, all he’s interested in is a bug the size of a pen-tip: the smaller European elm bark beetle.

St. Albert has swarms of bugs, but only a few are a threat to our forests. City officials put out traps each summer to spot them before they can eat our trees.

Sticky sentries

The two big pests Edmonton-area entomologists are watching for now are the smaller European elm bark beetle, which can carry Dutch elm disease; and the emerald ash borer, which is tearing through Canada’s ash trees at a frightening pace, says Mike Jenkins, biological science technician and bug guy for the City of Edmonton. Given that almost all of the boulevard trees in Edmonton and St. Albert are elm or ash, these pests are big threats.

St. Albert has about 10 bark-beetle traps similar to the one near Willoughby Clubhouse, Veenstra says. Although the city has never had a case of Dutch elm disease (nor has the province since 1998), these traps typically detect about five beetles a year that could carry the fungus that causes it.

These traps go to Edmonton for detailed study by entomologists, Jenkins says.

“It’s a fairly laborious task,” he says, as each trap can have thousands of suspect bugs, and you have to dig out and clean the glue off of each one. If it’s been wet out, you might also have to compete with maggots.

“You have to race the maggots to get to all the dead critters before they eat them.”

Once you’ve got the bugs under the microscope, you check their butts.

“They basically have a little trailer-hitch on their butt-end,” Jenkins says, and its shape will tell you if you have the right bug.

Should they spot any, crews go back to the trap site and look for elms that look damaged or dying, Veenstra says. Proper pruning can save them, but some might have to be destroyed.

St. Albert has four green triangular traps hanging amongst ash trees to spot the emerald ash borer, Veenstra says. These bugs are about a centimetre long and iridescent green, making them easy to spot. The bugs are drawn to the trap’s colour and pheromone packs and stick to their glue-covered surfaces. Crews have yet to find any in two years of monitoring, but plan to check some suspect trees near the Woodlands water park this summer for signs of larvae.

Stumble around the white spruce forest, and you might find Veenstra’s funnel trap. These traps draw in certain bugs with pheromones, whereupon they slip down interlinked funnels into a container of antifreeze for preservation.

One pest these traps detect is the mountain pine beetle, which is currently obliterating lodgepole and jack pine throughout western Canada. Jenkins says Edmonton traps have found about 13 of these bugs in the last two years, and scientists are scrounging local pine stands for the source. (You typically need hundreds of thousands of these beetles in one spot before they’re a problem, he adds.)

Another is the Asian longhorn beetle.

“It’s a scary looking thing,” says Veenstra, as it’s black with white spots, bigger than a dime and has antennas longer than its body.

These bugs such a threat that when they last showed up in Ontario crews clear-cut everything around them just to be safe, Veenstra says. The city would immediately call in provincial help if it spotted one of these beasts.

Jenkins encouraged residents to report any of these pests if they saw them, noting that every Asian longhorn beetle spotted in Canada so far has been detected by a resident, not a trap.

“The more eyes we’ve got out there, the better.”

Residents who spot strange bugs or sick trees should report them to public works at 780-459-1557. Inspection.gc.ca/pests has information on all the pests mentioned here.

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About Author

Kevin Ma

Kevin Ma joined the St. Albert Gazette in 2006. He writes about Sturgeon County, education, the environment, agriculture, science and aboriginal affairs. He also contributes features, photographs and video.