KEARNEY — Saving an ash tree from emerald ash borer beetles is a costly proposition, but an expert on the little green bugs that are creeping across Nebraska said some ash trees might be worth treating, even though most ash trees probably are better off removed.
“If you have one or two trees, look at them and evaluate what kind of condition they’re in. If they’re pretty healthy, if they’re a key tree in your landscape and provide good shade, these are good candidates for treatment,” said Laurie Stepanek of the Nebraska Forest Service.
The brightly colored emerald ash borer beetle that’s going to kill most of Nebraska’s ash trees arrived in the state in 2016.
“We knew it was going to be a very serious pest,” said Stepanek, who conducted her first workshop on the emerald ash borer invasion in 2003.
Emerald ash borer beetles are native to Asia, where trees have had centuries to develop natural defenses.
The green beetles are an invasive species in the United States, so trees aren’t genetically equipped to ward off the bugs. They leave eggs in the ash bark. Their offspring burrow into the bark and eat the soft tissue that carries nutrients and water in the tree.
The presence of the beetle in Kearney was confirmed in June. Last week, the city of Kearney launched a grant program to help property owners with the cost of removing their ash trees. This week, the Nebraska Department of Agriculture announced that beetles are in Washington and Seward counties in eastern Nebraska.
Other counties with the beetles are Cass, Dodge, Douglas, Lancaster, Otoe, Sarpy and Saunders.
Stepanek said property owners would be better off removing their ash trees if they exhibit signs of die back, or have damaged bark around the base from string trimmers or lawn mowers. It’s important to have a healthy tree at the base because that’s where chemical treatments are injected.
“Also look if there’s a lot of decay in the tree,” Stepanek said. “There may be mushrooms growing from the tree or hollow limbs or trunk.”
Tree owners know their ash is hollow if they see woodpeckers flying into and out of holes, or they observe insect holes, she said. “Those are indicators that the tree is stressed and not a good candidate for treatment.”
Owners also strongly should consider removal if their ash is growing in the wrong place and is likely to cause problems later. Trees close to sidewalks or under power lines will cause buckling of sidewalks as root systems expand. Also, trees under power lines could cause electrical outages when limbs blow into the lines and short out the power.
Cost for removal varies from the hundreds to thousands of dollars, Stepanek said, depending upon the tree’s size and whether it’s in a difficult location.
“It’s a dangerous job, not something an amateur should do,” Stepanek said.
She said treatments to counter emerald ash borer infestations cost about $200 for trees with a trunk that’s 20 inches in diameter. Treatments last two years, and then the treatment must be repeated.
Property owners considering treating their trees not only should evaluate the health of trees, but also if the trees are major components in their landscapes and are worth the multiple-year investment for treatments.
Stepanek said arborists drill holes around the base of the trunk to administer chemicals that help fight off the beetles. Treatments may protect trees, but drilling the holes damages and stresses them, so it’s better to do it in the spring. Trees then can recover during the summer.
Strong, healthy trees are the most likely to benefit from treatment, Stepanek said. The goal in treating a tree will be to help it survive the beetle infestation.
“The treatment should keep the trees alive until the other ash trees have died” and the beetle population has mostly disappeared, Stepanek said.
She said property owners should be careful about the companies they hire to remove trees or treat them.
“There may be people who come into town who never took down trees before. They may not have the credentials or training, so you have to investigate,” she said.
Tree services should be insured, and it’s helpful if they are certified members of the Nebraska Arborists Association or the International Society of Arboriculture.
Owners should dispose of their ash trees correctly, Stepanek said. “They certainly can burn the ash wood locally. Don’t give it away to anyone beyond that 10- or 15-mile zone.”
Property owners can find more information about the emerald ash borer on the Nebraska Forest Service website, nfs.unl.edu.
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