Emerald Ash Borer Discovered in 3 More Iowa Counties

Ash tree-killing beetle confirmed in Calhoun, Winnebago, and Worth counties

DES MOINES, Iowa (Aug. 9, 2021) – Emerald ash borer (EAB) has been found in Calhoun, Winnebago and Worth counties for the first time. This invasive insect has now been found in 84 of Iowa’s 99 counties since its first detection in 2010.

Insect samples were collected from Farnhamville (Calhoun County), Forest City (Winnebago County) and Manly (Worth County). Officials with the U.S. Department of Agriculture (USDA) Animal and Plant Health and Inspection Service (APHIS) confirmed these samples were positive for EAB.

EAB threatens all ash species. The wood-boring insect feeds on the inner bark tissue, disrupting the transport of water and nutrients. The cumulative damage of EAB feeding eventually kills the tree. Infested trees usually die within two to four years.

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 the adult beetle can fly short distances, people have contributed to the spread of this pest by moving infested material, including firewood. People are reminded to use locally-sourced firewood where it will be burned to help limit the spread of EAB and other invasive pests.

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 choose to 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. Spring, from mid-April to mid-May, is the best time to treat for EAB. 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.

See Iowa State University Extension and Outreach publication ENT57, Emerald Ash Borer Management Options, for more details about EAB treatment.

The State of Iowa monitors the 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 new location 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: 515-725-8453

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

For additional information, contact any of the following members of the Iowa EAB Team:

FAQs about Emerald Ash Borer - Updated 8/9/2021

Emerald ash borer found in Calhoun, Winnebago and Worth counties in Iowa

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About the Iowa Department of Agriculture and Land Stewardship

Led by Secretary Mike Naig, the Department of Agriculture and Land Stewardship serves the rural and urban residents that call Iowa home. Through its 14 diverse bureaus, the Department ensures animal health, food safety and consumer protection. It also promotes conservation efforts to preserve our land and enhance water quality for the next generation. Learn more at iowaagriculture.gov.

Media Contact:
Keely Coppess
Communications Director
(515) 326-1616           
Keely.Coppess@IowaAgriculture.gov