Inside Iowa State

Oct. 5, 2007

The green menace

by Erin Rosacker

It's not a matter of IF, it's a matter of WHEN. The Emerald Ash Borer is headed this way, and the little metallic green beetle is leaving no survivors in its wake. It is not particular in its destruction, attacking every ash tree species (green, white, black and blue).

Dubbed "The Green Menace" by the U.S. Department of Agriculture, the half-inch long borer is believed to have traveled from its native Eastern Asia and China to the United States in solid wood packing material. It was first detected in Michigan in 2002, and has spread to Ohio, Illinois, Indiana, Maryland, Pennsylvania and Ontario, Canada. It has killed 25 million ash trees, including more than 15 million in the hardest hit portion of Michigan.

"It's coming down the pike and when it comes, it will move across the state," said Mark Shour, ISU Extension entomologist. "This is an insect to be reckoned with. This is not Chicken Little."

ISU's plan

The Emerald Ash Borer (EAB) has not reached Iowa yet, but ISU is taking a proactive approach to the lurking threat, which has been found as close as 85 miles from the Quad Cities. Campus ash trees -- estimated at more than 1,200, excluding some woodland areas, recreation areas and Veenker Memorial Golf Course -- are being evaluated on a scale of one to five. Those rated on the poor end of the scale are being removed over the next few months. Culling stressed and weakened trees eliminates the specimens that attract the borer.

ISU's readiness plan also includes surveillance of purple sticky traps, inspection of suspect trees, experimenting with preventive insecticide treatments and eliminating ash trees from future landscaping projects. Plans for the disposal of infested trees, replacement of lost trees and funding for the project still are being fine-tuned.

Statewide response

State and Extension entomologists are monitoring Iowa's ash trees, which number more than 60 million and make up approximately 5 percent of the state's natural forest. Ash trees are located in all 99 Iowa counties and account for nearly half of the total trees growing in many urban areas.

Although the spread of the borer is estimated at a rate of one to two miles per year naturally, transportation of infested wood materials has hastened the borer's approach. These materials include coarse mulch, firewood, branches, logs and nursery stock. In a volunteer moratorium, commercial outlets and the public are asked to stop purchasing or transporting ash products from east of the Mississippi River.

Researchers are investigating ways to stop the spread of the borer, but Shour said a solution is likely five to 10 years from realization. For now, a liquid treatment poured on the ash tree's root zone may be a way of slowing the spread, a method that is most effective for young, uninjured trees. Homeowners are encouraged to start planting "companion" trees that will replace their ash tree casualties.

"In Iowa, we have been proactive. We are well ahead of the curve," Shour said. "Our citizens know a lot about it. Our plan could be a model."

What to expect

Currently, Iowa's EAB Response Plan requires close inspection of all ash species within a two-mile radius of an infested tree. If additional infestations are found, the search expands outward another two miles. If the Iowa Department of Agriculture and Land Stewardship (state entomologist's office) determines an infestation is sufficiently isolated, all the ash trees within two miles would be removed. State and federal quarantines are placed upon counties that contain infested trees, which prohibits the transport of ash products and firewood.

Removal of infested trees -- which can vary greatly in size and health -- requires the trees to be cut down, and the wood to either be destroyed (burning or chipping to a small size) or the main tree trunk and large branches to be de-barked. Since the borer does not burrow deep into the ash trees, the interior wood of larger trees can be used as lumber.

A cooperative effort among state and federal agencies and ISU Extension produced an informative Webcast covering the implications of the Emerald Ash Borer in Iowa. The Webcast is just one educational resource offered online by Extension's Pest Management and the Environment (PME) program.

"It's coming down the pike and when it comes, it will move across the state. This is an insect to be reckoned with. This is not Chicken Little."

Mark Shour, ISU Extension entomologist