It’s been 14 years since emerald ash borer (EAB), an invasive species of insect that kills ash trees, was first detected in Iowa. Now, with the latest confirmation of EAB in Emmet County, EAB has been detected in all 99 counties. The Emmet County samples were collected from a declining ash tree in Armstrong earlier this month by staff from the Iowa Department of Agriculture and Land Stewardship. The sample was then sent to the United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) for confirmation.
The larval stage of the EAB tunnels through the wood of ash trees just below the bark, which cuts off a tree’s ability to transport water and nutrients. The cumulative damage typically kills a tree within two to four years after becoming infested. There are several indicators of a potential infestation: 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. Once the EAB reaches its adult stage, it is approximately ½ inch long and a bright, metallic green.
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 37 states. In 2010, EAB was first discovered in Iowa in Allamakee County.
Now that EAB has been detected across the entire state, what can we do? To start with, 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. The course of action can either be a wait-and-see approach or involve the use of preventative insecticide treatments in order to preserve and protect the remaining healthy ash trees. The best time for that treatment is in the spring from mid-April to mid-May, as insecticides are the most effective when the ash tree is actively growing, and uptake is at its peak. Tree service companies can also 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.
Since EAB as well as other invasive pests can unknowingly hitchhike in firewood, people are still reminded to use firewood locally sourced from the area, where it will be burned to keep EAB and other tree-killing pests from being transported to new areas.
For more information on EAB, visit iowatreepests.com.
