Emerald ash borer detected in Douglas County, but options for ash tree owners are few
A quick drive down the main street of Kansas City, Kan., is all a person needs to see the effects of the emerald ash borer, said Marlin Bates, a horticulture agent at the Kansas State University Extension in Douglas County. The invasive insect, he explained, has already devastated the tree population on that historic stretch.
Symptoms of infected trees left untreated begin within the first year or two, and the mortality rate is 100 percent, Bates said. And at the end of September, the insects were detected in Douglas County.
“It’s just sickening what they can do to the ash trees,” Bates said.
The insects, which originated in East Asia, were introduced to the U.S. upper Midwest sometime around 2002, Bates said. And they’ve been in Kansas since 2012, but never before have they been this close.
On Sept. 30, the Kansas and United States departments of agriculture confirmed the presence of the emerald ash borer in Douglas County, Bates said. Fewer than 10 of the insects’ larvae were removed from a type of trap tree set in Eudora.
Bates said with the insect so close, it’s best to assume every ash tree in the county is in danger.
“We always recommend that anybody within 15 miles of a known infestation should consider their tree at high risk of infestation,” he said. “That means people need to figure out what they want to do with their trees.”
The insects lay their eggs on the trees, and once the larvae hatch, they burrow into the tree’s vascular tissue and begin to feed, Bates said.
“They start chewing away and create these serpentine canals, stripping the tree of its capacity to transmit water and nutrients,” he said. “And ultimately, through heavy infestation, that will strangle and kill the tree.”
How fast the insects kill the tree depends on many factors, Bates said. At first, the tree’s leaves will begin to thin, but within four or five years the plant might be totally dead.
The best way to combat the insects is with insecticides, Bates said, although they’re not 100 percent effective.
“There are insecticides that can be applied by homeowners, and we’d recommend those products to be used on trees less than 15 inches in diameter,” he said. “Anything larger than that, then a professional arborist should inject the insecticide.”
Treatments are most effective in the spring, Bates said. That’s when the larvae are small and more prone to the insecticides and the trees are taking in enough water to spread the chemicals throughout the entire plant.
Crystal Miles, horticulture manager for Lawrence’s Parks and Recreation Department, said in December that there are more than 1,000 ash trees in Lawrence parks and right-of-ways, and the city is trying to determine the best course of action for the impending insects.
Ash trees will need to be treated nearly every year, so owners wishing to go that route should consider the treatment a lifetime commitment, Bates said. If owners choose not to treat their trees, they should consider removing the tree before it becomes infected to prevent the spread of the insects, he added.
“If you have a tree that is affected and you permit it to stand there and die without doing anything at all, you’re perpetuating larger and larger populations throughout the years to exert pressure on your neighbors trees,” he said. “The responsible thing to do is to remove it and chip the wood.”
Treating, removing and planting trees might cost the city as much as $90,000 a year, Miles estimated.
If an ash tree holds sentimental value or a specific purpose, like providing shade or wind protection, but the owner doesn’t want to commit to an annual treatment, they also could consider planting a replacement tree, Bates said.
“You can certainly nurse along your ash tree for some time to prevent the ash borer from killing it,” he said. “Then when the replacement tree comes to some level of satisfactory size, that would be a good time to stop treatment, remove the ash tree, or both.”
Help identifying ash trees, recognizing the insects and treatment options can be found online at douglas.k-state.edu.