Five insect larvae with characteristics that are consistent with the emerald ash borer have been found in two sentinel trap trees in Allamakee County. The larvae were collected on Oct. 25 in trees at Pool Slough and in Black Hawk Point Wildlife Area, south of New Albin.
These additional discoveries do not change the quarantine on moving wood from Allamakee County currently in place, but provides additional evidence of the invasive tree-killing pest’s location in the state.
“This is significant because the Black Hawk Point discovery is the furthest west infestation that we found,” said Tivon Feeley, with the Iowa Department of Natural Resources forest health program. This is also the first time emerald ash borer has been found in a sentinel tree in the state.
There are 80 of the 416 sentinel trees across the state left to check as part of the annual emerald ash borer surveillance effort.
The natural progression of the beetles by flight is estimated to be 2 to 5 miles per year, but moving infested ash material enables the beetles to move farther and faster. Based on information from Michigan, Ohio and Indiana, the presence is usually discovered a few years after the beetle becomes established.
The metallic green beetle causes its damage during its larval stage, a creamy-white legless flat worm up to one inch long. Larvae feed on the living tissue under the bark of ash trees, cutting off the pipelines of nutrients, minerals and water to the tree, and causing a slow death.
Residents within 15 miles of the latest finds who have ash trees on their property will have a decision to make to either use a preventive treatment from an arborist to save the tree or to wait for the borer to find the tree.
When choosing an arborist, make sure, at a minimum, that they are a member of an organization like the National Arborist Association, Iowa Arborists Association or the International society of Arboriculture or the American Society of Consulting Arborists. These organizations certify and offer continuing education training for their members.
Simply having a chainsaw and a truck (or insecticide treatment equipment) does not qualify someone as an arborist and homeowners are encouraged to do their homework, regardless of who they hire.
“Arborists are usually really busy and don’t have time to go door-to-door soliciting business,” said Emma Bruemmer, state urban forester for the DNR.
Preventive treatments include a springtime application of an insecticide directly to the ash tree or into the root zone of the tree. Larger trees may require a fall treatment as well. The DNR is discouraging aerial application to minimize the unintended impacts of the insecticide on nontarget insect populations, such as honey bees and natural enemy insects.
“We are discouraging homeowners who live more than 15 miles from the infestation from treating their ash trees with insecticides to protect them from this pest,” Feeley said. “Unfortunately, we are hearing reports of individuals distributing incorrect information promoting treatments across the state. It is unnecessary to treat healthy ash trees beyond 15 miles from a known infestation.”
Iowa State University Extension and Outreach has a list of recommendations for homeowners dealing with emerald ash borers at: