Stingless Wasps vs. Emerald Ash Borer: Iowa’s Strategy to Save Ash Trees

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FAIRFIELD, Iowa - The Iowa Department of Agriculture and Land Stewardship is fighting fire with fire.

Or rather, it's fighting invasive species with invasive species.

"Nature is fighting nature here," said Mike Kintner, the Emerald Ash Borer Regulatory Coordinator with IDALS. "This is a classic case of bio-control, where we're taking a natural enemy from EAB's native homeland - which is in Asia - bringing it here to North America, and introducing it out into the wild."

The Emerald Ash Borer is an invasive pest that has now plagued more than half the United States, laying its eggs in and feeding off of the country's ash trees.

"Emerald Ash Borer is having a huge impact on cities," Kintner said. "We've stressed the fact that do a tree inventory, find out how many trees are there that are ash trees, so you can plan accordingly. Because once it moves into a community, there's quite a rapid curve of death with ash trees."

Kintner says some experts call the Emerald Ash Borer the most destructive invasive species in U.S. history; formally discovered first in Michigan in 2002, some experts suggest it could have been in the U.S. a decade earlier. The pest came from its homeland in Asia via wooden packaging materials shipped overseas, and since its arrival has spread across 26 states.

But now, there's an answer. And it's a tiny wasp. Kintner says not to fret - these parasitic wasps are the size of a pinhead and don't sting. Their larvae feed off Emerald Ash Borer larvae. Bringing them from Asia and into the U.S. is a biological solution to fighting off an invasive epidemic. Iowa is the 24th state to participate in this federal program, and IDALS workers like Kintner are now releasing these wasp eggs into the Whitham Woods, in Fairfield, as a starting point.

"Last week was the first time we set up these ash bolts here in Iowa for the parasitic wasp release, to help battle Emerald Ash Borer," he said. "This particular one, the parasitic wasps are actually in here developing in this piece of wood. So, we'll go out and hang these in ash trees - today we have 12 of these that we'll hang out in ash trees - and as they mature underneath the bark, they'll chew their way through and fly off. And the thought is they will go in and start to infect and kill off other Emerald Ash Borer."

But the road to Hell is always paved with good intentions, and some worry the good intentions of releasing these wasps will lead us to the same conclusion we've reached before when introducing invasive species. For example, in 1788, rabbits were introduced to Australia as a source of food; they quickly reproduced, and drastically affected the country's ecology and crops. In 1876, kudzu was introduced in Mississippi to combat erosion; now, it's taken over the South, spreading 150,000 acres a year. And in 1937, nutria were brought from South America to Louisiana for the fur trade, but they escaped and began wreaking havoc on the southern marshland ecosystem.

So, how do we know we won't regret releasing these Asian wasps down the road? Kintner says the homework has been done.

"There's been a lot of testing. With people, it does raise concern that we're releasing an insect not native here to the United States," he said. "But keep in mind, there's been a lot of testing done with researchers and scientists, these have gone through quite the process to make sure they're not going to have a negative impact on our beneficials and native insects here. There's been permits done, environmental assessments, so due to the rigorous testing, we feel pretty comfortable that this is going to be safe for Iowa and will benefit in the fight against Emerald Ash Borer."

But Kintner wants to clarify - this solution won't save the ash tree in your front yard; rather, this strategy is meant to curb the continued reproduction of Emerald Ash Borer in Iowa, and hopefully, save the future ash trees to come.

"I don't think Emerald Ash Borer will ever be gone completely," he said. "They'll come into a level where they're in the landscape, but hopefully not doing the damage they are in today's world. So, you know, with checks and balances in the natural world, I think the two will work to balance each other out."

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