Johnson County residents prep for emerald ash borer
Josh O’Leary, Iowa City Press-Citizen
When the emerald ash borer was found in Cedar County last fall, it only added to the urgency locally to prepare for the inevitable arrival of the invasive insect that has wiped out millions of trees in the U.S.
On Tuesday, experts led a pair of programs for Johnson County professionals and homeowners about how to identify the east Asian beetles, how to inspect ash trees for signs of damage and what preventative treatment options exist.
Mike Kintner, an entomologist for the Iowa Department of Agriculture and Land Stewardship, said the emerald ash borer has the potential to be even more destructive than Dutch Elm Disease, which devastated the U.S. elm tree population last century.
“So far the emerald ash borer has killed millions of ash trees, and it will continue on killing millions more,” Kintner said in a presentation at the Johnson County Extension office. “We’re not even close to experiencing the full damage of this pest.”
Emerald ash borers are small, metallic-green beetles that are about a half-inch long and an eighth-of-an-inch wide — one can fit easily on a penny. The insects, native to Asia, first was found in the U.S. in Michigan in 2002 has since killed tens of millions of ash trees in 13 states.
The insect was first detected in Iowa in 2010 and has since been identified in nine counties, including eight since 2013. The beetle was discovered in Mechanicsville in Cedar County in October.
Iowa is home to some 55 million ash trees, including nearly 3 million in urban areas — most of which are expected to be wiped out by the insect in the coming decades, experts say. The pest could cost cities millions in removal expenses of ash trees in public right-of-ways and parks. Ash trees, once infested, can become brittle and present falling hazards.
Mark Shour, an entomologist with Iowa State University Extension, said the insect can be difficult to spot because its telltale damage — the “D” shaped holes where the beetles emerge, the notching of leaflets, bark being stripped away — doesn’t occur initially at eye level.
“This insect always hits the top part of tree and goes down,” Shour said. “That’s why early detection is hard.”
Regular chemical treatments can stave off the insect for individual trees using a variety of methods, including soil injections, soil drenchings, bark sprays and trunk injections. Treatments generally need to be applied annually, though Shour said the tree must be in good health, and cities and property owners need to decide if the tree is worth preserving.
“The trees you want to save need to be a benefit to the owner or the town,” he said.
While property owners have the option of treating their trees, the DNR does not recommend doing so unless the pest has been found within 15 miles. The site of the Cedar County infestation is about 30 miles from Iowa City.
Shour said in the insect’s first five or six years after its introduction to an area, the damage can be slow to manifest. After that period, however, the number of trees affected spikes dramatically.
“Just because people are not seeing the massive deaths of ash trees at one time at the beginning of infestation doesn’t mean it’s not coming,” Shour said.
Reach Josh O’Leary at 887-5415 or firstname.lastname@example.org.