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Emerald ash borer confirmed in Mitchell County

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Emerald ash borer (EAB) has been discovered in Mitchell County for the first time. Since its original detection in 2010, the invasive, ash tree-killing insect from Asia has now been confirmed in all but six of Iowa’s 99 counties.

Ash Tree

Ash trees scheduled for removal on the MercyOne North Iowa Medical Center campus in Mason City show unmistakable signs of emerald ash borer damage. Infected trees are dead at the top with brown streaks on the trunk indicating larvae damage as they eat their way through the tree.


According to the press release, EAB larvae were collected near Spring Park in rural Osage by the Iowa Department of Agriculture and Land Stewardship. Federal identification confirmed the samples were positive for EAB.

EAB is a significant threat to native ash tree species, typically killing a tree within two to four years after becoming infested. The cumulative damage by the larvae (immature stage) feeding on the inner bark eventually kills ash trees. The feeding cuts off the tree’s ability to transport water and nutrients.

Indicators of an infestation may include canopy thinning, leafy sprouts shooting from the trunk or main branches, serpentine (“S”-shaped) galleries under the bark, bark splitting, woodpecker damage, and 1/8-inch D-shaped exit holes.

While adult beetles can disperse locally by flying, long-distance spread of this insect is attributed to people moving infested material, including firewood. People are encouraged to use locally-sourced firewood where it will be burned to help limit the spread of EAB.

According to the press release, now is the time to decide a course of action for ash trees at risk of EAB attack (within 15 miles of a known infestation). Landowners and managers can wait and see what happens, remove declining ash trees and replace them with other species, or use preventive insecticide treatments to preserve and protect valuable and healthy ash trees.

The best time to treat for EAB is in the spring, from mid-April to mid-May. Insecticides are most effective when the ash tree is actively growing and uptake is at its peak. Tree service companies can apply insecticide trunk injections through the summer if soil moisture is available.

Iowa State University Extension and Outreach has produced a publication about EAB treatments. For more information, download Emerald Ash Borer Management Options,

The State of Iowa continues to evaluate the potential spread of EAB on a county-by-county basis. Before a county can be declared positive, a life stage of the insect must be collected and confirmed. Anyone who suspects an infested ash tree in a county not currently known to be confirmed with EAB is encouraged to contact one of the following:

• Iowa Department of Agriculture and Land Stewardship, State Entomologist Office, 515-725-1470

• Iowa State University Extension and Outreach, Entomology, 515-294-1101

• Iowa Department of Natural Resources, 515-725-8200

Additional information on EAB, including a county detection map, can be found at

In addition, Mitchell County's Extension office in Osage, 315 Main Street, will be hosting a free informational meeting concerning EAB from 6-7:30 p.m. on Tuesday, Oct. 4. For registration and more information, contact the office at 641-732-5574 or email Darla Olson at Those interested are asked to register in advance.

The meeting will be presented by Dr. Donald Lewis, professor emeritus and former Extension entomologist for ISU; Mike Kintner, EAB and spongy moth coordinator for the Iowa Department of Agriculture and Land Stewardship; and Greg Heidebrink, district forester for the Iowa Department of Natural Resources.

Topics will include how to identify EAB, signs of infestation, pesticide treatment and replacement options.


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