Invasive Wasps Released to Battle Invasive Beetles

Photos: David Cappaert - Michigan State University, guano / cc

To the untrained eye, all may appear tranquil and calm in Wisconsin's forests, but the truth is that a war of sorts is underway -- between two foreign species on U.S. soil. For the last several years, a particularly nasty invasive beetle has been ravaging ash trees, and in the latest bid to combat the destructive pests, entomologists have enlisted the beetle-killing prowess of other non-native insects -- tiny parasitic wasps recruited from China. Experts are hoping the wasps will fight the good fight to save the ash trees without causing any problems of their own.The antagonistic insects in this battle royal are emerald ash borers. They were first discovered in the United States back in 2002, likely arriving in shipping containers from their native China. Since then, they've devastated ash forests in states across the country by burrowing beneath the bark of trees where they feast and hatch their larvae -- which ultimately kills the tree after around two years.

So far, some tens of millions of trees have been killed in the onslaught; they're just not adapted to defend against the invasive pests.

Chemical treatments have proven to be effective in staving off the emerald ash borers, but they are used primarily in residential settings. To tackle a forest full of the foreign invaders would require a living, breathing solution -- something that could hunt down the beetles and end the tree-eating party. And to find it, entomologists looked to the very place from whence their problem emerged.

Researchers from the US visited China in search of a species to combat borers, and they returned with three types of parasitic wasps known to prey on the problem pests. The wasps have then been released into the some isolated places where the invasive insects have been most devastating. Recently, in the diminishing ash forests of Wisconsin, entomologists from the University of Wisconsin-Madison have begun setting loose hundreds of the beetle-hungry wasps.

The only problem is, no one is entirely sure that they aren't creating a whole new invasive species dilemma. In a report from The Northwestern, UWM professor Ken Raffa discusses the future of the regions unwelcome inhabitants:

Scientists know from researching the wasps that they kill the ash borer. What they don't know is whether the wasps will take hold in the wild, reproduce on their own and help keep the emerald ash borer in check.

That, they say, could take years to determine.

"There's no way it will completely solve the emerald ash borer problem," Raffa said. "That insect is here to stay. What we are hoping is it could slow down the spread of the insect, maybe reduce its impact or maybe even assist with the recovery of ash once the outbreak has passed through."

This summer, the university team plans on releasing even more tiny wasps into the forests, that according to a report from Milwaukee's Journal-Sentinel. But while questions still remain about the long-term effect of the purposefully released foreign insects -- just what sort of impact they'll have on staving off the emerald ash borers is still up in the air as well.

"How much bang are we going to get for these little guys?" asks Wisconsin Department of Natural Resources scientist Andrea Diss-Torrance. "We don't know right now."

Follow me on Twitter or Facebook.
More on Invasive Species
Invasive Species: When Small Creatures Do Big Damage
Species of Invasive Fish Walk on Land, Climb Trees
Invasive Species a Growing Problem in Antarctica

Tags: Insects | Wisconsin

Best of TreeHugger 2014

WHAT'S HOT ON FACEBOOK