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Ash trees in distress: What to do

Published: Wednesday, Jan. 15, 2014 10:50 a.m. CDT • Updated: Wednesday, Jan. 15, 2014 11:05 a.m. CDT
Mark Shour, center, Iowa State Extension entomologist, talks to area property owners after a public meeting about the emerald ash borer held Thursday at Supertel Inn and Conference Center. The destructive insect has been positively identified in Creston.

Editor’s note: This is the third in a three-part series on the emerald ash borer and how to tell if a tree has been attacked, prevention and treatment to stop or slow the spread of the destructive beetle.

Once an ash tree is infested by the emerald ash borer (EAB), nothing can be done.

But, there are treatment options for healthy ash trees.

Mark Shour, Iowa State Extension entomologist, talked about treatment options to prevent EAB during a public meeting Thursday evening at Supertel Inn and Conference Center.

Shour said EAB generally will start in an older and weaker trees.

“Once infested, it’ll stay infested. Eventually it will die. Once the large one is dead, it’ll hit the little ones,” said Shour. “If you have a sickly tree, don’t think about treating it — only healthy ones.”

Don’t panick

Shour said do not remove an ash tree until it is infested and, even then, to wait until it is dead or decaying. He said the wood from a dead ash is still usable for firewood and furniture building. But, in quarantined areas the wood cannot be moved out of the quarantined area.

Shour said, since the adult emerald ash borer does not fly a great distance, it could be 15 to 25 years before some ash trees in the area are affected.

Residential homeowners have two options for applying treatments to healthy ash trees — soil drench and granular.

The active ingredient in the soil drench product is imidacloprid or imidacloprid plus clothianidin and is used to treat trees up to 60 inches, or 20 inches diameter at breast height (dbh). The granular product contains dinotefuran, imidacloprid or imidacloprid plus clothianidin and is for trees up to 36 inches, or 12 inches dbh.

“You don’t want to apply these during the winter,” said Shour. “The best time to treat is when the tree is functioning, not when it’s asleep.”


Shour said treatment is only to be done on trees within a 15-mile radius of an infested tree once it has been positively identified.

An infested ash tree has been positively identified in Union County near the center of Creston, therefore any ash tree in Union County is eligible to be treated.

“Based on what they found, it’s been here about three years,” he said.

Some products are applied in the spring, some can be applied either in the spring or fall.

“You can only treat once a year,” Shour said. “If you treat in the spring, you can’t do it again in the fall.”

Most products will need to be applied yearly. Only one product, Tree-Age, is good for two years, and it requires application by a certified professional.

Shour said these chemicals will not kill birds or bees, but will kill caterpillars that eat ash tree materials. But, he added, if there are flowering bushes under a treated ash tree the flowers will be toxic to bees.

“Read the product label carefully before you buy it,” he said. “Application is based on the size of the tree. More is not better.”


Shour said a professional can also be hired to treat the trees or remove them, but, he said, “be a wary consumer.” There may be people who say they can treat, trim or remove the trees, but if they are not certified professionals, you could be the victim of a scam.

“Get written estimates,” he said. “And check vendor references.”

Shour said even with treatment EAB can spread.

“Is this product guaranteed? Absolutely not,” he said. “It’s considered to be 95 percent effective, but there’s no guarantee. Generally, the thinking is they do a pretty good job of controlling the emerald ash borer.”

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