K-State Research and Extension News
September 20, 2012
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Monitor Ash Trees for Emerald Ash Borer

Pest Kills Infested Trees Quickly

MANHATTAN, Kan. – The first case of emerald ash borer in Kansas should encourage Kansans to monitor their ash trees.

The pest has been in southwest Missouri since 2008 and was recently identified in Platte County, Mo., in July, said state Extension forester Charles Barden with K-State Research and Extension. It was not a surprise then when the beetles showed up on the other side of the border last month in Wyandotte County.

“Once the insects are in the tree, it will die within a couple of years,” Barden said.

The adult beetles deposit eggs in crevices of a tree’s outer bark. Then newly emerged larvae bore through the bark to begin feeding on the tree’s inner tissues. “As the borers grow in size and number, they disrupt the sap flow of the tree,” Barden said. “It will look sickly for several years before it dies.”

The adults usually emerge in late spring to early summer, leaving small “D-shaped” holes in the tree trunk. Typically the tree canopy will start thinning from the top, and as much as half of the branches may die within the first year of being infected.

Barden said the risk of spreading the infestation is greatest when firewood from infected ash trees is transported to new areas. It is illegal to move ash firewood out of a county like Wyandotte, where emerald ash borer has been identified.

People who have ash trees within a 15-mile radius of a known infestation might consider initiating preventive insecticide treatments, according to Bob Bauernfeind, horticultural entomologist with K-State Research and Extension.

“Preventive treatments are best undertaken while trees appear healthy and their vascular transport systems are in tact,” he said. “Treating a tree already showing symptoms of emerald ash borers is rarely effective.”

Typically the vascular system in these trees has been too damaged to allow the insecticide to reach the trunk, branches and canopy. Barden said early spring is usually the best time to treat ash trees against emerald ash borer.

Both Barden and Bauernfeind encouraged people within a 15-mile radius of a documented infestation or within the same county as an infestation, to carefully consider which ash trees are worth treating. “Homeowners must determine the value and worth of a tree on their property, and what costs they are willing to incur in terms of preventive treatments,” Bauernfeind said.

Some treatments require a licensed arborist to apply the insecticide, which is an additional cost. Barden said these treatments usually provide longer protection.

Barden advised homeowners to remove unhealthy ash trees, since they tend to attract emerald ash borers. He also warned against planting new ash trees for now.

For more information about emerald ash borer, visit with your local Extension agent.


K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by: Bethany Sanderson
K-State Research & Extension News

Charles Barden - cbarden@ksu.edu - 785-532-1444