- Associated Press - Saturday, October 4, 2014

DENVER (AP) - Emerald ash borer has a new enemy in Colorado: A parasitic wasp, one of three such species that preys on the ash-killing borer beetle in its native China.

An interagency team planned to place pieces of wood containing the pupae of about 2,000 Tetrastichus planipennisi wasps in trees in Boulder, The Denver Post reported (http://tinyurl.com/mpw22kj ).

The wasp specifically targets the larvae of the bright-green, ash-tree-killing insect now found in 24 states and two Canadian provinces. It was identified in an ash tree in Boulder almost exactly a year ago.

When the gnat-sized, stingerless wasps hatch - roughly in a few weeks - the females will sense the borer larvae under the ash bark and drill into them to lay as many as 100 eggs in a single, inch-long borer larva. When they hatch, the wasp larva will eat the borer larva from within, killing it in about a week and continuing to feed on its corpse.

“We can get up to four wasp generations in a year,” said John Kaltenbach, a biocontrol specialist for the Colorado Department of Agriculture.

Tetrastichus was chosen over another wasp species for two reasons, Kaltenbach said. It can tolerate Boulder County’s potential for cold winters, and the timing is right, with the borer larvae starting to be active within ash trees.

The wasps are coming from Michigan, where they are being grown in quantity. Colorado is the 19th state to receive the wasps.

A second wasp species that parasitizes emerald ash borer eggs will be introduced next year, when eggs are on the trees.

The wasps and other biocontrols won’t eradicate the insect that has killed tens of millions of trees in the Midwest and East, Mitch Yergert, director of the Colorado Department of Agriculture’s plant industry division, said in a news release Monday.

“Biocontrol is an exercise in patience,” Kaltenbach said. “This is playing the long game. If four or five years from now, we have trees that are still standing (because of the wasp), we’ll say it was a big success.”

The cost of releasing the wasp on the University of Colorado’s East Campus - about $2 per insect - came from the USDA and U.S. Forest Service biocontrol budget, Kalt-enbach said. The cost to Colorado mainly comes in staff time for the multiple agencies that will manage it, including the state agriculture department, the city of Boulder and Boulder County, the University of Colorado, Colorado State University and the state and federal forest services.

The wasps are stingerless - what looks like a long, thin stinger is actually its egg-laying organ, or ovipositor - and not attracted to pets or people, the USDA said.

But it’s hoped that they will be deadly in defense of the swath of Boulder where emerald ash borer has been found.

It’s the borer larvae that kill ash trees. When enough larvae create enough tunnels, an ash tree can’t feed or water itself. Systemic pesticides can save some trees that are only partially damaged and kill the larvae that begin eating previously uninfested trees.

But they aren’t cheap, and as emerald ash borer spreads to most Front Range cities’ urban forests, treatments are expected to have a big effect on city budgets.

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Online:

Identifying ash trees, the insect, help for home and property owners: eabcolorado.com

Firewood restrictions and recommendations to limit ash borer movement: dontmovefirewood.org

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