Emerald Ash Borer Confirmed in Palo Alto County

Ash tree-killing insect now confirmed in all of Iowa’s counties except Emmet County

April 1, 2024, 10:00 am |

Contact: Don McDowell, Iowa Department of Agriculture and Land Stewardship, 515-326-1616, don.mcdowell@iowaagriculture.gov

Emerald Ash Borer Side View by moneycue_canada/stock.adobe.com.DES MOINES, Iowa – The United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service has confirmed the presence of the emerald ash borer in Palo Alto County for the first time. Insect samples were collected in March from an ash tree in Basswood Recreation Area outside of Emmetsburg. Department staff noticed woodpecker damage in an ash tree, which is a symptom of an EAB infestation. The sample was then submitted to USDA for analysis and test results confirmed the presence of EAB.  

EAB is a non-native, wood-boring insect threatening all species of ash trees. The adult EAB beetle is approximately one-half inch long and metallic green. The larval stage of this insect tunnels through the wood just beneath the bark of ash trees, cutting off the tree’s ability to transport water and nutrients. The cumulative damage typically kills a tree within two to four years after becoming infested. 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.

EAB was unknown to North America until its discovery in southeast Michigan in 2002. The invasive, ash tree-killing insect from Asia has now been found in 36 states. In 2010, EAB was first discovered in Iowa in Allamakee County. Emmet County is now the only remaining county in Iowa without a detection.  

Landowners with ash trees on their property should begin to consider a course of action for at risk trees, which are generally those within a 15-mile radius 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.

While EAB travels only short distances on its own, people aid in its long-distance movement. Since this insect can unknowingly hitchhike in firewood, people are reminded to use locally sourced firewood where it will be burned to keep it from being transported to new areas.

The State of Iowa continues to track 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 Emmet County 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.

More information about EAB, including detection maps, is available at iowatreepests.com.

Photo credit: moneycue_canada/stock.adobe.com

Shareable map: Emerald Ash Borer Treatment Consideration Areas in Iowa