As the specter of the emerald ash borer continues its seemingly inevitable spread across the state, an Iowa State University professor is working with communities and homeowners to prepare for life without ash trees. The emerald ash borer, an invasive beetle that attacks and kills ash trees, has been confirmed in eight Iowa counties, putting city officials and property owners across the state on high alert for signs of the small green pests.
Jan Thompson, an ISU professor of natural resource ecology and management, says upwards of 240 Iowa communities have begun systematic inventories of the trees that populate parks and other public spaces as a first step in determining what eventually will replace ash trees.
ISU forestry prof helping Iowans prepare for decline of ash trees
Thompson is advising those communities to get a head-start on the ash borers by filling in existing empty spaces with a diverse array of tree species. She said diversity is the key to protect against future pests that target a particular species, like the emerald ash borer does with ash trees. "Hedge your bets and plant some of everything," she says. "Diversity is critical because you don't know what the next pest will be. Mix it up."
Thompson estimated that about 15% of the trees in Iowa parks and public spaces are ash trees. They're popular because of their large canopy, a feature that provides a number of advantages such as shading structures, absorbing water during wet weather and storing carbon.
Species that offer a similar canopy and are suited to environmental conditions in Iowa include American basswood, honey locust, sugar maple, black maple, red oak, white oak, bur oak, and sycamore trees, she says.
About 15% of trees in Iowa parks and public spaces are ash trees
But Thompson emphasizes, that choosing a tree species also depends on the specifics of the site and other qualities like drought and flood tolerance, mature tree height and spread, as well as growth rate. Thompson says some municipal forestry departments are considering the preemptive removal of ash trees before the appearance of emerald ash borers, but she says it's probably not necessary for homeowners with ash trees to take such a precaution.
That holds especially true if the tree is in good health and providing shade and other important functions, she notes. In that case, homeowners may want to investigate treatment options that can protect the tree from the borer. "If you have old and damaged ash trees, or a tree that's likely to become a hazard, it might be good to have it removed," she adds. She also encourages Iowans to be on the lookout for signs of emerald ash borers, including small D-shaped holes in tree trunks and splits in the bark.
Eight counties in Iowa have confirmed EAB infestations
Emerald Ash Borer, or EAB, has been positively identified in a residential tree in Eddyville in Wapello County, and trees in the public right-of-way in Waverly in Bremer County on February 12, 2014. That's the latest confirmation. EAB kills all ash tree species and is considered to be one of the most destructive tree pests ever seen in North America.
The EAB infestation in Eddyville was found by a citizen who reported suspect ash trees to an Iowa Department of Natural Resources (DNR) regional forester. With the assistance of the Iowa EAB Team, larvae were found, and positively identified by federal identifiers as EAB. A certified arborist hired by the City of Waverly to do a tree inventory discovered larvae in declining ash trees along two city streets. The larvae were positively identified by federal identifiers as EAB.
A statewide quarantine restricting the movement of hardwood firewood, ash logs, wood chips and ash tree nursery stock out of Iowa into non-quarantined areas of other states was issued on Feb. 4, 2014.
"The winter months provide an unobstructed view of the condition of the branches and main stem of ash trees, allowing for a clear view of woodpecker activity and insect damage on the trees," says state entomologist Robin Pruisner of the Iowa Department of Agriculture & Land Stewardship. "I won't be surprised if more infestations are found in Iowa before we shake the final snow from our boots and trees leaf out this spring."
Iowa EAB team cautions people to obey statewide quarantine
The Iowa EAB Team provides EAB diagnostic assistance to landowners and includes officials from Iowa Department of Agriculture and Land Stewardship (IDALS), Iowa State University Extension and Outreach, the Iowa Department of Natural Resources (DNR), USDA Animal Plant Health Inspection Service and the USDA Forest Service.
The Iowa EAB Team strongly cautions Iowans not to transport firewood across county or state lines, since the movement of firewood throughout Iowa or to other states poses the greatest threat to quickly spread EAB even further. Most EAB infestations in the United States have been started by people unknowingly moving infested firewood, nursery plants or sawmill logs. The adult beetle also can fly short distances, approximately 2 to 5 miles.
Contact Iowa EAB Team members to have suspicious looking trees checked. The State of Iowa will continue to track the movement of EAB on a county-by-county basis. Before a county can be officially recognized as infested, an EAB must be collected and verified by USDA entomologists.
To learn more about EAB and other pests that are threatening Iowa's tree population, please visit the Iowa Tree Pests website. Or, for more information contact any of the following members of the Iowa EAB Team:
Robin Pruisner, IDALS State Entomologist, 515-725-1470, [email protected]
Paul Tauke, DNR State Forester, 515-242-6898, [email protected]
Tivon Feeley, DNR Forest Health Coordinator, 515-281-4915, [email protected]
Emma Hanigan, DNR Urban Forest Coordinator, 515-281-5600, [email protected]
Mike Kintner, IDALS, 515-725-1470, [email protected]
Jesse Randall, ISU Extension Forester, 515-294-1168, [email protected]
Mark Shour, ISU Extension Entomologist, 515-294-5963, [email protected]
Laura Jesse, ISU Extension Entomologist, ISU Plant and Insect Diagnostic Clinic, 515-294-0581, [email protected]
Donald Lewis, ISU Extension Entomologist, 515-294-1101, [email protected].
Jeff Iles, ISU Extension Horticulturist, 515-294-3718, [email protected]