Northwest Iowa — An invasive insect that’s been destroying trees for many years has reached another county in our area, and one nearby.
Emerald ash borer (EAB) has been found in Ida and Sioux counties for the first time. The invasive, ash tree-killing insect from Asia has now been confirmed in all but 13 of Iowa’s 99 counties since its original detection in 2010. The other county in our four-county area with the confirmed sighting of the beetle is Lyon County.
The beetle’s larvae were removed from ash trees in Galva (Ida County) and Sioux Center (Sioux County) by an Iowa Department of Agriculture and Land Stewardship employee. Officials with the USDA Animal and Plant Health Inspection Service (APHIS) confirmed the identification of the larvae.
According to the Iowa Department of Ag, the adult beetles of this insect feed on ash leaves, causing very little damage. It is the cumulative damage by larvae feeding on the inner bark that eventually kills ash trees. They say the feeding cuts off the tree’s ability to transport water and nutrients, typically killing a tree within two to four years. EAB is a significant threat to all ash species.
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, say Iowa Ag Department officials.
They say that while EAB can travel locally by natural means, the long-distance spread of this insect is attributed to people 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.
The ag department says that 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 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 a county not currently known to be confirmed with EAB is encouraged to contact the Iowa Department of Agriculture and Land Stewardship, State Entomologist Office: 515-725-1470, Iowa State University Extension and Outreach, Entomology: 515-294-1101, or the Iowa Department of Natural Resources: 515-725-8453.
Additional information on EAB, including a county detection map, can be found at iowatreepests.com.
