It's here.

The emerald ash borer, which has laid waste millions of ash trees in the U.S. Midwest and western Ontario, has been found in London.

It's timing for the unwanted arrival could not be worse: the Forest City is already worrying how to cope with its dwindling tree cover that gives the city its nickname.

The tree-destroying beetle was found Oct. 24 by the Canadian Food Inspection Agency in two infested trees on a private lot near Wonderland Road and Springbank Drive, within a kilometre of Springbank Park, the crown jewel of the city's park system. Worse, the federal agency suspects the beetle has been on the site at least two to three years.

With an estimated 10,000 ash trees alone in its parks and along its boulevards, even more counting private property and city-owned woodlots, London could be a veritable smorgasbord for the beetle with no known predators.

"It could be anywhere," said Gerry Dowding, project manager for the CFIA, who delivered the grim news to city council last night.

"Probably by spring, we'll have a better idea of what we're dealing with," Dowding said.

Coun. Joni Baechler called the potential fallout for London a "massive" problem.

"It could put us back substantially in terms of tree and woodland cover," she said.

Thought to have arrived in North America from China in wooden packing crates, the borer has left once tree-lined stretches of some American cities looking like war zones.

In a bid to slow or halt the borer's advance, from Michigan and east through Ontario, the Canadian Food Inspection Agency mounted elaborate defences which the pest has overcome:

- A ban was slapped on the movement of ash firewood and still the borer advanced.

- A controversial ash-free zone was cut near Chatham, creating a kind of fireline officials had hoped would prevent the beetle's eastward advance and which triggered an outcry by property owners who saw their trees -- in some cases, huge lots -- levelled.

"The fact it's 10,000 trees in the most obvious areas of the city is a concern to us," said Dave Leckie, the city's director of roads and transportation. "We have entire streets lined with ash trees."

Dowding said the London infestation was likely caused by the delivery of fire wood or other human intervention.

"It's highly unlikely the insect arrived here on its own," he said, adding there's no proven method of controlling the spread of the beetle.

An inspection of trees within 500 metres of the now-quarantined London site showed no signs of the beetle.

Mayor Anne Marie DeCicco-Best said she's buoyed the infestation appears limited.

"We're ahead of the curve on this compared to . . . other municipalities," she said.

Dowding said the beetles are dormant and won't spread any farther until spring.

EMERALD ASH BORER

- Native to China, Japan, Korea, Mongolia, Taiwan and the Russian far east. Believed to have arrived in North America in pallets, crates or other wooden shipping materials.

- Though similar to native American borers, this insect is surprisingly aggressive and is killing reasonably healthy ash trees stressed by drought and disease.

- Afflicted trees grow along streets or in woodlots and range from five centimetres in diameter to sawmill-sized timber.

- The borer appears to kill all ash species -- green, white, red and black -- but not other trees.

- The emerald borer does its deadly work by laying its eggs on the bark or in bark crevices. The insect larvae hatch and tunnel beneath the bark, creating cavities in the actively growing wood. Once the insect has girdled the stem, cutting off the flow of nutrients, the tree dies relatively quickly -- within a year or so of being infested.

- The tree dies from the top down. Foliage wilts and the canopy thins.