Serious risk to the trees of the cities

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The caterpillars, gypsy moths have completely stripped these trees of their leaves. Subjected to such treatment during two or three consecutive summers, the trees are weakened. More vulnerable to diseases, they die.

Anne Caroline Desplanques

Sunday, 24 September 2017, 08:00

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Sunday, 24 September 2017, 08:00

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An insect pest from Europe, that devours the trees of Toronto and of the New England high-speed, is a threat to the urban forest of Montreal already taken by assault by the emerald ash borer.

This insect is a moth called ” european gypsy moth “. Its caterpillars have devoured a tree about three to Massachusetts this spring and forced Toronto to proceed with the aerial spraying of biopesticides in the middle of the city.

Present in North America since the end of the 19th century, there has never been significant damage in Quebec. But last year, the division of plant protection of the canadian Agency of food inspection has captured 539 specimens of european gypsy moth in Quebec only, learned The Newspaper. This is more than in any other province of the country.

“It is an insect always threatening, because it eats anything. It is very polyphagous. In addition, these caterpillars have hair very stinging, so it is annoying from the point of view of public health “, says Éric Bauce, an entomologist at the faculty of forestry of Université Laval.

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Each female moth gypsy moth can lay up to a thousand eggs from which emerge as many of the caterpillars. At maturity, they are each 6 cm and a single can devour one square metre of foliage.

Not much interested in conifers, the european gypsy moth is not of concern to the commercial forest in quebec, the boreal forest, ” says entomologist Timothy Work, the Centre for forest research, UQAM. However, it presents a serious risk to the urban forest, ” he said.

Economic problem

“It is much more difficult to calculate the economic impact that it would for the timber, but it is huge,” says the entomologist. Imagine if half of the trees in your neighborhood were dying. Imagine the impact on the value of your property, on your quality of life. “

“It is an economic problem which will be transferred to the owners of the houses “, he adds.

Mr. Work points out that the emerald ash borer already weighs heavy in the pocket of the taxpayers. Since 2011, the City of Montreal has spent$ 30 Million to the fight against the emerald ash borer.

This south of the border since the end of the 19th century, the european gypsy moth already costs $ 3.2 billion $ US per year in North America, according to an analysis published in the scientific journal Nature Communications.

Global warming

This cost will increase with the warming climate, which favours the multiplication of insects, provides for the same study.

The ministry of Forests has placed the european gypsy moth on its list of species to monitor in the context of climate change, says the entomologist of the department Pierre Therrien.

“It is difficult to predict how it will evolve, but it is reasonable to assume that there will be an increase of the population “, said the scientist.

The population of gypsy moths is directly related to winter conditions, ” says Mr. Bauce. Most winters are mild and snowy, the more gypsy moths survive and can therefore grow more of a spring to the other.

Pests illegal imported by boat

The increase in shipping traffic in the St. Lawrence exposes quebec’s forests to another gypsy moth much more dangerous than the one who came from Europe : the asian gypsy moth.

“It’s going to hit us much harder than climate change. It is a problem that is gigantic, ” warns the entomologist Timothy Work, the Centre for forest research, UQAM. For him, it is not a question of whether the asian gypsy moth is going to happen with us, but when.

Attracted by the lights of the boats, the female gypsy moths come to lay their eggs on the containers of goods. The eggs travel so secretly and hatch at the end of the crossing. The larvae are quickly dispersed in the wind.

The pest made regular breakthroughs in the port of Vancouver, which is directly turned towards Asia. There has until now never been detected in Quebec, but scientists from the department of Forests have to the eye.

“It worries us, because, unlike its cousin, the european, the female of the asian gypsy moth is flying. It therefore has the capacity to affect large areas quickly, ” says the entomologist Pierre Therrien, the ministry of Forestry.

Buffet boreal

In addition, the insect asian loves conifers. The boreal forest would therefore be a giant buffet for him.

Already very affected by the budworm the spruce, the commercial forest in quebec would have little resources to protect themselves from an infestation of gypsy moths from asia.

“We consider that the alien bugs have a very great potential of destruction, because there are no predators, a natural barrier to their spread,” explains Dr. Therrien.

Control deficient

The protection of our forests depends on the diligence of the federal government, which has the power to control the ships entering canadian waters.

But according to Mr Work, ” we don’t have really good control policies “. Moreover, it is by ships from Asia loaded with wooden crates infested, ” he says, that the emerald ash borer arrived in North America.