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This insect from China is wreaking havoc on Ontario's ash trees

Dangerous invasive bug killing thousands of trees in Canada

Leeanna McLean
Digital Reporter

Wednesday, August 24, 2016, 2:17 PM - It's the summer and thousands of trees are bare in southern Ontario. Experts say a green beetle with a big bite is to blame

The emerald ash borer (EAB) is an invasive species that lives in ash trees. Native to China, they are about half an inch in length and were first introduced to Canada in 2002. Emerald ash borers have killed ash trees in more than 260,000 hectares of Ontario forests. Because there are no natural predators, the Canadian Forest Service (CFS) says the beetle kills up to 99 per cent of ash trees in infested areas.

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While the insect eats away at foliage, it's the larvae that does the boring. The young tunnel beneath the bark and feed on the layer of live cells between the bark and sapwood, cutting off nutrients and water to the upper portions of the tree. Unfortunately, the intense heat this season is not helping matters.

Heat contributing to the problem

"Since the emerald ash borer is cool blooded, if the temperature becomes warm sooner, then the insect becomes active sooner in the season and will grow larger, faster and mate sooner," Brian McKelvey, city arborist for Burlington, Ont., told The Weather Network.

As the temperature rises, the larvae also becomes active for longer periods during the day, McKelvey added.

"The drought has put the ash trees under huge amounts of stress. The trees cannot produce naturally chemical defenses against the insect."

The presence of EAB in Burlington was first confirmed in 2010 and now the beetle has been identified in numerous pockets across the city, according to McKelvey. Burlington's population of ash trees, which make up about 14 per cent of the urban forest, is at danger of being completely destroyed. 


Since 2011, officials have been treating ash trees with an insecticide called TreeAzin, which has been registered for use across Canada. The insecticide contains a natural product called Azadirachtins, originating from Neem tree seeds. TreeAzin is injected directly into the tree in early summer, significantly reducing larval growth, feeding and egg viability, according to Natural Resources Canada (NRC).

Oakville has the most aggressive EAB management program in the country, NRC reports, with 75 per cent of the municipal tree canopy treated with the insecticide as of 2011.

"The product has been very effective at conserving the ash canopy, with all but one of the 5,700 treated trees remaining alive," John McNeil, manager of Forestry Services, Parks and Open Space in Oakville told NRC back in 2013.

Meanwhile, 6,000 trees have been recently treated with TreeAzin in Burlington. It does not have a negative effect on wildlife as it is a natural product and is injected into the tree from a pressurized system, meaning it's not released anywhere into the atmosphere, said McKelvey.

Courtesy: BioForest Technologies Inc.

Another method involves releasing parasitic wasps. The CFS announced last Wednesday 1,600 of the non-stinging wasps native to China, will help control the population of emerald ash borers in Ontario and Quebec. There are plans in place to release the wasps nine times over the summer.

Two species will be introduced. The wasp larvae feed exclusively on ash borer eggs and larvae.

"They don't want to eat anything else. So even if you give them no choice but some other species they basically won't eat and they'll just die," Dr. Krista Ryall, senior research scientist with CFS told CTV.

Supplied by the U.S. Department of Agriculture, the parasitoids have been released at various sites across the country since 2013 including, Ottawa, London, New Market, Gatineau and Montreal.

The wasps do not pose any risk to the environment and are not harmful to humans.

Tetrastichus planipennisi -- one of two species of parasitic wasp used to control EAB in North America

Cutting down ash trees

This year's drought has exacerbated the EAB problem and often times ash trees are under so much stress they lose the battle against the beetle.

"The emerald ash borer attacks the cambium layer, which is responsible for moving water up and down the tree. If you combine that with the drought where there is limited water resources available, the ash trees are really, really stressed out and you can see it," Andrew Avsec, urban forestry coordinator with Hamilton's Naturalist Club told The Weather Network. "The decline this year is quite significant."

The city of Hamilton is cutting down 2,300 trees per year with 11,000 removed since the $26.2 million EAB program first began, The Hamilton Spectator reports.

City removal is focused on municipal parks and streets with home owners left to pick up the financial burden of removing ash trees on personal property. 

How much does it cost to get rid of your ash tree? 

There is no set price as it depends on size and location, according to McKelvey. Some reports indicate it can cost homeowners from $350 to $1,000 to remove dead ash trees.

Burlington resident Jenna Dobson just had her tree cut down several weeks ago.

"I moved here for the trees, so I was really devastated when they [city officials] said they were going to cut it down. I asked for them to wait a little longer, but branches kept falling all over the lawn and I was worried about my kids and something happening to them. So, that's when I contacted them and changed our course of action," Dobson told The Weather Network.

Once the ash tree is removed, the stump remains until a new tree is planted the following year.

"Trees in cities are very important, especially in these dry and hot conditions because we need the shade to make cities livable," said Avsec. "I think we just need to refocus ourselves as society to put a very, very high priority on our forests and just loosen up the resource purses when it comes to management of forests and leaving healthy forests for the future. We need to put the resources forth to understand this because as global warming becomes more and more of an issue, and we are seeing the effects now, our forests are what are going to make our communities livable in changing climates."

SOURCE: NRC | The Hamilton Spectator | CTV

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