The emerald ash borer (EAB) has been positively identified in a residential tree in the city of Creston, the county seat of Union County, according to the Iowa Department of Agriculture.

The sighting makes the fifth location where the invasive beetle has been found in Iowa.

EAB kills all ash tree species and is considered to be one of the most destructive tree pests ever seen in North America.

The Union County EAB infestation was found when an arborist contacted state officials about a suspect ash tree. Investigation by the Iowa EAB team revealed the beetles’ characteristic galleries and D-shaped exit holes in dead branches, and a partial adult beetle was positively identified by federal identifiers.

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), US Department of Agriculture (USDA) Animal Plant Health Inspection Service and the USDA Forest Service.

EAB infestations were previously discovered in Allamakee County in May, 2010, Des Moines County in July, 2013, Jefferson County in August, 2013 and Cedar County in October, 2013.

"I think we’re seeing the culmination of an EAB population that is finally large enough to detect, coupled with trees readily showing symptoms because of multiple stresses in recent years, including EAB, drought and floods," said State Entomologist Robin Pruisner of the Iowa Department of Agriculture and Land Stewardship.

A quarantine covering 25 counties in eastern Iowa was issued on Nov. 1 in an effort to slow the accidental movement of EAB by humans. An additional quarantine in response to the Union County infestation is being developed.

A quarantine restricts movement of hardwood firewood, ash logs, wood chips and ash tree nursery stock out of the quarantined counties.

The Iowa EAB team strongly cautions Iowans not to transport firewood across county or state lines. The movement of firewood throughout Iowa or to other states poses the greatest threat to the quick spread of EAB.

Most EAB infestations in the US have been caused by people unknowingly moving infested firewood, nursery plants or sawmill logs.

The adult beetle also can fly short distances, approximately two to five miles.

Ash is one of the most abundant native tree species in North America and has been heavily planted as a landscape tree in yards and other urban areas.

According to the USDA Forest Service, Iowa has an estimated 52 million rural ash trees and approximately 3.1 million more ash trees in urban areas.

It is unknown how many public and residential ash trees are located in Creston.

State Forester Paul Tauke said, "Forestry Bureau staff with the Iowa Department of Natural Resources have completed 242 urban tree inventories in Iowa, in communities with less than 5,000 residents."

Statewide, Iowa averages 16-17 percent ash on city property, though the ash component can get as high as 87 percent, Tauke said.

"There is no inventory for Creston, but we hope this latest infestation will motivate communities that have not taken an inventory of their forestry resources to do so very soon," he said.

ISU Extension and Outreach Entomologist Mark Shour said, "Preventive treatments next spring — mid-April to mid-May, 2014 — are available to protect healthy and valuable ash trees within 15 miles of the known infested area."

For more details, see www.extension.iastate.edu/Publications/PM2084.pdf.