On the lookout for an invasion of tree-eaters

Dr. Mark Shour points out the winding path where larvae of the Emerald Ash Borer ate away at a tree under its bark. Shour was in Le Mars Tuesday leading a workshop on how to identify and control the spread of the insect. [Click to enlarge]

They're moving in on Iowa.

Emerald Ash Borers, insects that kill ash trees by eating away at them under their bark, are heading this direction, according to Dr. Mark Shour, a program specialist on pest managment and the environment from Iowa State University Extension.

Shour was in Le Mars Tuesday teaching locals to identify the insect and its destruction, and he said northwest Iowans have reason to be concerned.

"It's not in Iowa yet, but we expect it at any time," he said, holding up a case with a few of the bugs preserved in it. About the size of a small house fly, the adults are irridescent green -- thus the "emerald" in their name.

"They've already destroyed 25 million trees in the core zone: Michigan, Indiana and Ohio," Shour said. "It's spilled into Illinois, with the closest being Peru, Ill., which is only about 85 miles away from Iowa's Quad Cities."

The larvae of the Emerald Ash Borer feed underneath the bark in the living tissue, slowly killing the tree by cutting off the flow of water, nutrients and minerals.

Adult borers only eat the leaflets of the trees.

"If you've got an ash tree, watch for a branch dying high in the crown or a woodpecker working the top of the tree only," Schour said. "The borer hits the top of the tree first and goes down."

People can also check for borers by looking for sprouts growing around the trunk or exit holes in the bark shaped like a capital letter "D" in the bark, about 1/8 inch in diameter. Owners can peel back the bark and look for the curvy trails left behind by the larvae.

If people see any of the signs, Shour said, call ISU Extension or the district forester to have them take a look at the trees.

Infested trees can be sprayed or have insecticide injected, but these methods have only proven to offer 40-95 percent control, he said.

"The only guaranteed way (to control the spread Emerald Ash Borers) is to cut the tree down and burn it or chip it," Shour said.

If the tree owner wanted to cut down the tree and use the wood for lumber, they could do that as long as they remove all the bark and a half-inch of wood.

"After that, they can use the wood for anything," Shour said.

Emerald Ash Borers are often spread to new areas by humans transporting infested wood, he explained.

"If someone from Michigan came here to Le Mars to camp and brought a couple pieces of firewood, they could bring the borers," he said.

The insects can travel themselves by flying, although they can only spread about five miles from the source at a time.

Part of the reason Shour is putting on presentations like the one Monday in Le Mars is to multiply the number of people watching for the insect's invasion into Iowa trees.

"The sooner we find them, the better it is," he said. "A small population is much easier to deal with than a large one."