A natural experiment to head off a devastating tree-killing beetle began Thursday in heavy woods well off the Des Plaines River trail in northeast Lake County.
Wearing waders to navigate what had become a swampy target area, staff of the Lake County Forest Preserve District coaxed nearly 1,000 tiny predator wasps out of plastic cups and onto a dozen trees infected with the emerald ash borer.
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"It was a successful release," declared Matt Ueltzen, restoration ecologist. "Whether they'll be successful remains to be seen."
The little predators, known as parasitoids, can't bite or sting and are of no harm to humans or animals.
But those involved in what has become a multifaceted battle with the destructive metallic green beetle hope the imports from a federal research facility in Brighton, Mich. can help slow its spread.
"They'll find the emerald ash borer larva and lay their eggs on the larva or inside the larva," Ueltzen said.
The theory is adult wasps will lay eggs alongside the emerald ash borer larvae, and the developing wasps will consume the borer before it can cause damage. It is expected to take years to find out if that happens.
"These are a lot more host specific so they'll concentrate on attacking the emerald ash borer," Ueltzen added.
Two species of wasps, Spathius Agrili and Tetrastichus planipennisi, released Thursday, are about the size of an ant and a poppy seed, respectively.
A third species is said to be so small it is difficult see. Two more releases are planned in coming weeks, as part of a long-term U.S. Department of Agriculture initiative.
The trick is to establish a healthy population of the wasps so they can keep the emerald ash borer population in check naturally.
Including trees that have been cut down as a preventive measure, the emerald ash borer is responsible for the demise about 25 million ash trees in North America.
It was first identified in the U.S. in 2002 near Detroit and has spread to 15 states and Canada. In Illinois, the emerald ash borer has been identified in 20 counties and about 200 communities, including nearly two dozen in Lake County, according to the Illinois Department of Agriculture.
The site in the Sedge Meadow Forest Preserve near Wadsworth is in an area of Lake County that has been hit hard.
"It's in all four corners (of Lake County) and the center," explained Mark Speckan, forestry crew chief for the forest preserve district. "When it will explode, we don't know."
It was confirmed about two years ago at the district's ThunderHawk Golf Club, where a few hundred ash trees have been removed as a result.
The emerald ash borer feed below the bark and cut off nutrients. Damage occurs from the top of the tree down, which is why it can go unnoticed for years.
"It basically just strangles the tree," Speckan said. "A lot of people have the (emerald) ash borer in their trees and they don't realize it."
In China, federal researchers several years ago found parasitic wasps that evolved with the emerald ash borers and attack the beetles' larva and eggs.
They were brought to the U.S. and studied under quarantine for about four years at a research facility in Michigan before being approved by the USDA for release in 2007. The agency produced and distributed 165,000 wasps in 2010.
Since 2009, foresters in Chicago have released the wasps at 15 sites as part of a multipronged effort to defeat the pests.
"We try to call them biocontrol insects," explained said John Lough, a Chicago city forester. "What we're focusing on with the study is to establish the wasps."
Lough said he is optimistic, as one species of wasp has become established at an early site. Test results are pending on others.
"Anything we can do to make EAB something that has its own natural predators," will help in the fight against the pest, he added.
The use of biocontrol is not new to Lake County. About 10 to 15 years ago, a type of beetle was released at several locations to combat purple loosestrife, an invasive plant.
"It really did work," said Allison Frederick, environmental communications specialist with the forest district. "That's what we're hoping for here."