June 8, 2009
UI arborist, DNR officials advise public to watch for Emerald Ash Borer
An invasive beetle that feeds on and eventually kills ash trees has Iowa officials scouring northeastern Iowa after an Emerald Ash Borer larva was found in a tree at the Osborne Welcome and Nature Center in Clayton County, according to state officials.
Infestation has not been confirmed but could cause substantial damage on the University of Iowa campus, with notable areas of ash trees including the east side of the Main Library and the north and south sides of the Pentacrest, according to UI campus arborist Andy Dahl who works in UI Facilities Management.
"Unfortunately, there is no preventative at this time," Dahl said. "There are injectable and basal insecticides that are effective but are costly, and have to be applied every year or two."
The most recent confirmed Emerald Ash Borer infestation was in Victory, Wis., a town just across the Mississippi river from the northeast Iowa border, in April.
The beetle is emerald green, half an inch long and about a 1/8 inch wide. It kills all ash (Fraxinus) species by larval burrowing under the bark and eating the actively growing (cambium) layers of the trees.
Mark Vitosh, district forester at the Iowa Department of Natural Resources, said the problem is that officials can't identify an infected tree until it begins to show symptoms of infestation.
"We don't have a system to find this critter until it begins attacking trees," he said, noting setting traps has had limited success.
The UI campus has between 700 and 800 ash trees on maintained areas of the campus, roughly 10 percent of the population, Ash trees also make up about 10 percent of Iowa City's public tree population. The state of Iowa has an estimated 88 million ash trees, about 20 percent.
Vitosh said Iowa residents need to be the eyes and ears of the state by calling the DNR when they suspect a tree may be infested. He also emphasized the importance of buying firewood locally.
Dahl said depending on how severe the initial outbreak is, all control strategies are still on the table.
"We need to continue to diversify tree species in our urban forests and have better inspection at points of entry so we aren't dealing with problems similar to Emerald Ash Borer in the future," Dahl said, who works in UI Facilities Management.
Residents should look for die-back, which is dying branches and leaves and woodpecker activity at the top of the tree. Ash trees are characteristic of their opposite branching and compound leaves, usually with more than seven leaflets. Iowa City and UI campuses management have been trying to defend against infestation by no longer planting ash trees and removing distressed or dying ash trees before the problem arises.
"The ash tree will get significantly thinner in the upper canopy for three to five years prior to actual die-back," Dahl said. "There is also increased sprouting at the base of the tree; these are call suckers or watersprouts. Also, with the increase in woodpecker activity, is the 'blonding' of the bark in the upper canopy of the tree, where the bark wears away from all the woodpecker activity, another good way to identify the Emerald Ash Borer."
Vitosh added that there are steps people can take to help curb the spread of Emerald Ash Borer.
"It is key that people do not bring firewood from other states into Iowa. That is the number one spreader of the pest," Vitosh said.
The beetle, native to China, Japan and Korea, was first discovered in North America in Michigan in the summer of 2002. It has since spread to 10 other states and Canada.
Officials from the Iowa Department of Agriculture and Land Stewardship, Iowa State University Extension Office, Iowa Department of Natural Resources, USDA Animal Plant Health Inspection Service, and the USDA Forest Service have created the Iowa Emerald Ash Borer Team to educate the public about the risks of the beetle and how to prevent its destruction. Their efforts are directed at businesses that sell firewood and people that would transport firewood across state lines.
STORY SOURCE: University of Iowa News Services, 300 Plaza Centre One, Suite 371, Iowa City, Iowa 52242-2500