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An invasive, wood-boring beetle that is deadly to ash trees has been officially spotted in all 99 Iowa counties.
The emerald ash borer was first spotted in Eastern Iowa in 2010. Emmet County was the last county without an emerald ash borer sighting, until Thursday, Oct. 17.
Mark Vitosh, the Iowa Department of Natural Resources district forester, said once the main wave of the infestation makes its way through all of Iowa, it will leave behind millions of dead ash trees.
Vitosh said he anticipates the main wave of the emerald ash borer to hit Iowa within the next five to 10 years.
"In many locations in Eastern Iowa and other parts of the state, there has already been significant ash loss," Vitosh said, adding that most ash trees in Eastern Iowa are either dead or dying if they are not treated for the insect.
According to the Iowa Department of Natural Resources, early inventory data indicates there are roughly 52 million woodland ash trees and 3.1 million community ash trees in Iowa.
Vitosh said ash trees in Eastern Iowa have been hit harder than other parts of the state, but the infestation has headed westward.
"That zone of death and how quickly trees are dying is pretty significant in Eastern Iowa, and it slowly kind of moved across the state," Vitosh said. "The western part of the state is now seeing massive death, which we've been seeing for the last five to 10 years in Eastern Iowa. It just took longer to get there."
Vitosh said since there has already been significant loss in Iowa, fewer ash trees will die going forward since the remaining trees will be limited.
Also, ash seedlings are trying to establish in Iowa's woodlands, and it's unknown when those trees could become infested.
"As long as there are some non-treated living ash present, there will be a food source to maintain some population of the emerald ash borer, so this issue could linger for many years," Vitosh said.
Since the insect was initially detected in Iowa about 14 years ago, the Iowa Department of Agriculture and Land Stewardship has been tracking and recording the known locations of the emerald ash borer throughout the state.
"The known whereabouts of emerald ash borer has helped landowners and managers make more informed decisions for at-risk trees, which are generally those within a 15-mile radius of a known infestation," said Mike Kintner, an entomologist with the department.
Despite the threat the insect poses, there are both treatment and preventive measures Iowans can take to protect their ash trees.
But before treating an ash tree, Vitosh said landowners and homeowners should make sure their tree is a good candidate for treatment by getting it assessed by an arborist. He said a tree that may not be a solid candidate for the treatment could be a tree with weak branches or a weak trunk, despite looking structurally healthy.
Specifically, to be a candidate for treatment, an ash tree must have less than 50 percent canopy thinning or less than 30 percent of its branches dead.
An infested ash tree can be treated two ways: commercial injections of insecticides into the base of the tree, or homeowners themselves can buy insecticide from a home store or nursery and pour it around the tree.
Trees treated by injection have be treated every two years, while trees with the pour method have to be treated annually. Vitosh said the insecticide poured around the tree does not work for trees greater than 20 inches in diameter.
Preventive insecticides are available as well, but they are only effective before damage to the tree starts, according to Iowa State University's Extension and Outreach program.
Vitosh said one challenge of the ash tree after it dies is that is becomes brittle, posing a risk to people and property.
Although ash trees degrade in value and strength once they become infested with the beetle, Vitosh said the wood can be used as firewood.
But since firewood is a common way the insect travels from region to region, experts say consumers should always purchase firewood locally.
The beetle, originally from northeast Asia, was first discovered in North America in 2002 but was likely introduced to the U.S. in the 1990s, according to the National Park Service.
Vitosh said the emerald ash borer initially traveled to Iowa after being spotted in Wisconsin, near Iowa's border.
"It was just a matter of time before it got there," he said. "Being just across the river, it could have been carried across into Iowa through firewood, through nursery stock, or it could have flown in."
Kintner said the beetle can only fly short distances. "The human-assisted movement of emerald ash borer in firewood contributes to an increased rate of spread," he said.
Kintner said other tree-killing pests lurking in firewood also can hitchhike in firewood and be introduced to new areas, again emphasizing people should "source firewood locally."
Vitosh said it's likely the beetle also traveled to Iowa by "hitchhiking" on railroad cars.