Photo: Iowa Department of Natural Resources
(Kossuth County, IA) -- An ash-tree killing pest has now been found in all but 7 of Iowa's 99-counties. The latest Emerald ash borer detection is in Kossuth County, in northern Iowa. The Iowa Department of Natural Resources says Emerald ash borer typically kills ash trees within two-to-four years.
EAB was first detected in Iowa in 2010.
The DNR says the tree dies due to cumulative damage by the larvae (immature stage) feeding on the inner bark. The feeding cuts off the tree’s ability to transport water and nutrients.
Signs 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.
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.
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.