Amazing little buggers
Non-stinging wasps from China introduced to Ottawa to help slow spread of emerald ash borer

ottawasun.com
By Julienne Bay
August 30, 2015

One sticky August morning, just before noon, Dr. Barry Lyons disappears into a densely forested area off a major road in south Ottawa.

He's walking briskly through a bed of poison ivy, following neon-coloured tape that's wrapped around tree trunks.

"The actual work only takes about 10 minutes," laughs Lyons, who had driven all the way from Sault Ste. Marie.

Lyons is a forest entomologist for Natural Resources Canada's Great Lakes Forestry Centre, and has worked to bring a Chinese parasitoid into Canada to help control the emerald ash borer, the scourge of trees across this city and elsewhere.

Emerald ash borer was first confirmed in Ottawa in 2008, and its spread has resulted in the removal of 15,678 ash trees in the city between 2009 and 2014 -- that's just the number of trees removed by the city alone.

Ottawa is one of five sites in Ontario where a foreign species of non-stinging wasp are being released to fight the emerald ash borer.

There are two types of parasitoid wasps approved in Canada for release: Tetrastichus planipennis, which attacks emerald ash borer's larvae, and Oobius agrili, which attacks the eggs.

Both species are originally from China and work in similar ways: They use their ovipositors (what looks like stingers, but aren't) to stick their eggs inside a host.

The Tetrastichus parasitoid's hatching larvae feed on the larvae of the emerald ash borer. Similarly, the egg-attacking Oobius agrili parasitoid lays its egg on the ash borer's eggs, eventually destroying its host.

All this is similar to something out of the movie Aliens, Lyons says.

The larvae parasitoid was first approved by the federal government in 2013, while the egg parasitoid was approved for use this year.

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Back in that densely forested area in south Ottawa, Lyons removes a few palm-sized pieces of wood that hang from wires at the sides of selected ash trees and installs three new pieces of wood. The new pieces contain the larvae-attacking parasitoids. One piece of the barkwood has more than a hundred of the predators inside.

The larvae-attacking parasitoids are released three times in early summer and three times in late summer.

It means a lot of driving for Lyons, as he goes to sites across Ontario.

"They'll fly out and merge naturally (into the eco-system)," he says. "We do the releases in the natural forested areas."

The egg-attacking parasitoids are released three times in mid-summer, using another device called "oobinators." These are MacGyvered pharmacy pill cases that have pieces of coffee filters inside. On the filters are the eggs of the parasitoids.

The oobinators are hung on the trees, using twist-ties. The pill cases are left open with a mesh cloth on the bottom of them. That's where wasps can crawl out after hatching, to integrate into the ecosystem.

"It's a very simple device, but sleek," Lyons says.

15,678 trees lost to borer
Since emerald ash borer was first confirmed in Ottawa in 2008, 15,678 ash trees have been removed from municipal property.

It’s unknown which area of the city has been most affected or how many trees have been removed by other privately-owned tree services.

Emerald ash borer is a type of a beetle, which spends most of its one-or-two-year life cycle under the bark, laying eggs around late May to early June. Once larvae finish feeding under the bark, they mature into adult beetles that chew their way out of the tree.

According to Bill Gardiner, owner of the Gardiner Tree Trimming & Removal, it takes about two years for infested trees to show symptoms.

Gardiner, who’s been in the tree business for more than four decades, said half of the calls he gets concern ash trees in the Ottawa area.

About two years after becoming infected with emerald ash borer, the tree’s top branches usually die first - and by the time the infection becomes obvious, it’s often too late for the tree to have any chance of survival.

By the third year of infection, the tree’s branches have no leaves, and there are flat spots outside of the bark, which are actually small holes where emerald ash borer lay the eggs and eat the interior wood. The bark eventually falls off.

While there are injections available to treat the trees, Gardiner said that can be very costly, as the treatment needs to be done every two years.

For infected trees smaller than 4 inches, it makes no “economic sense” to treat them, he said. For large trees, on the other hand, it’s cheaper to treat the tree than to cut it down, he said.

Gardiner also said homeowners with infected trees often wait until it’s too late.

“People think if a few branches are missing leaves, it’ll grow back,” he said. “People leave the treatment until it’s too late...it’s fatal.”

Facts about the two predators

• Both Tetrastichus planipennis (the larvae-attacking parasitoid) and Oobius agrili (the egg-attacking parasitoid), are originally from China. Canada imports them from a biological control production facility in Brighton, Mich.
• Another species of larvae parasitoid, Spathius agrili, was also approved for use in Canada, but were deemed unfit to survive in Canada's climate.
• The egg parasitoid is less than a millimetre in length, while the larvae parasitoid is about three millimetres long. What appear to be stingers are actually ovipositors, devices used to stick their eggs inside their host.
• The egg-attacking parasitoid is parthenogenic, which means it does not need male to reproduce. Larvae-attacking parasitoids need males to reproduce, on the other hand - but the number of males being released is very small.