Treatment can help save ash trees

Good news for those who want to protect trees from insects

-Messenger photo by Lori Berglund
Jaime Brinkman, left, and Will Vaughn of Smitty’s Lawn and Landscape with an ash tree undergoing treatment for emerald ash borer. The bottle on the ground holds a small amount of insecticide that is injected directly into the tree. The procedure can be completed in a matter of hours and protects and treats a tree for two years.

Ash trees — basically being starved of water and nutrients by the emerald ash borer –are dying.

How about a little good news? The ash trees don’t all have to die.

There is hope, and there is a treatment that can save towering ash trees that are treated with safe and approved insecticides injected by certified applicators, according to Jaime Brinkman, ISA certified arborist for Smitty’s Lawn and Landscape in Fort Dodge.

“The treatment we recommend is an injection with a chemical called emamectin benzoate,” Brinkman said. ‘It does not deter the pest from getting on the tree, but if you have an infestation coming into your area you can help fight it off.”

Treatments are done every two years and can be started before there is any visible damage to an ash tree. With the speed that the EAB is sweeping across Iowa, even healthy-looking ash are likely to already be infected, especially in most of central Iowa.

Hamilton County saw its first report of EAB in 2018. By 2020 EAB was in Webster County. Wright, Pocahontas and Calhoun counties started reporting cases in 2021. Humboldt, and Kossuth counties reported their first cases earlier this spring.

“The emerald ash borer has moved from the southern part of Iowa up to the northwest counties,” said Brinkman. “There are only seven counties now that don’t have confirmed emerald ash borer.”

A native of east Asia, EAB is a small wood-boring beetle. It was first detected in the United States in Michigan in 2002. EAB arrived in Iowa in 2002 and has been creeping its way across the state ever since. The metallic green beetle lives outside the tree and feeds on leaves. But the adults are not the problem, according to Brinkman.

“The larvae are what actually damages the tree,” she said.

The larvae reside under the bark, tunneling into the phloem and cambium layers, which are responsible for delivering water and nutrients to the tree. The activity of the larvae essentially starves the tree to death.

“It can kill a tree in a matter of three to seven years,” Brinkman said.

Look up high for the first signs of damage. Infected trees will see a thinning of the canopy.

“A lot of times, emerald ash borer will hide in a tree for up to three years before we really see symptoms,” Brinkman said. “We can treat a tree until there is about a 30 percent canopy decline and have really great success.”

“We don’t recommend waiting until you see a 30 percent decline in canopy,” Brinkman added.

The treatment window is open now, because ash trees need to be treated from about May to mid or late September, while there are leaves on the tree.

The treatment is surprisingly simple. Don’t expect heavy equipment pulling up to the yard because it all comes in just one small bottle of insecticide that is injected directly into the tree, meaning there is no chemical drift.

Will Vaughn is a certified applicator for Smitty’s Lawn and Landscape and described the procedure.

“First, we identify the size of the tree and determine the number of injection sites and the amount of chemical that we need to put inside the tree,” he said.

Vaughn looks for root flares, or places where the root juts out just a bit indicating a strong area of the root zone for feeding of the tree. Tiny holes are drilled and a small plug is inserted to guide the chemical into the proper areas of the tree to target the larvae. After treatment, the holes are barely noticeable. The whole procedure may take only a few hours.

“Our main goal is to get that chemical into that layer of the tree where it needs to go so that it will translocate throughout the tree,” he said. “The larvae come across the chemical, ingests it, and it kills off the larvae.”

The only visible sign that the tree has been treated will be a small tag, or badge, for record-keeping purposes. Of course, the more important sign that it has been treated will be the fact that it keeps its leaves.

An ash tree treated proactively two years ago by Smitty’s in Fort Dodge is showing little to no sign of infestation. A neighboring ash tree, on the same side of the street, subject to the same conditions, has begun to show signs of thinning canopy. Fortunately for that ash tree, it got its first treatment this month, and because the canopy decline has not gone too far, Brinkman and Vaughn expect good results.

“This treatment is both proactive and curative,” Brinkman said.

Treatments will continue every two years until the EAB has finished its work of decimating the untreated ash population.

“It will move out when it has no food supply, and then we can stretch these applications out to maybe three years,” Brinkman said..

As an invasive species, EAB does not have a true natural enemy in the local environment. But woodpeckers do prey on the larvae. That’s why flecking, or the damage caused by woodpeckers, is another sign of an infestation. But while folks may cheer on the woodpecker for trying to put a dent in the population of EAB, they alone cannot save a tree.

Bird lovers will ask, will this treatment sicken birds, especially the woodpeckers who dine on the larvae? Fortunately, the Iowa Department of Natural Resources has good news on that front, calling it “unlikely.”

Woodpeckers eat only live larvae, so they do not consume the chemical. If larvae look tasty to a woodpecker, then it hasn’t been treated. Furthermore, dead larvae break down very quickly, according to the DNR. And because these chemicals are not fat-soluble, they do not “bio-accumulate in animals.”

The DNR pointed to Michigan and Ohio as examples of success, noting that those states have been using such injected insecticides for several years and there have been no reported cases of woodpecker poisoning as a result.

Emamectin benzoate is derived from a naturally occurring soil bacterium and has actually been used to treat fleas on pets for number of years. It’s also used to control pests in cotton and vegetable fields.

Sadly, the DNR has a grim outlook for untreated ash trees in Iowa. They are almost certain to go the way of elm trees that were wiped out by Dutch Elm disease in the 1970s.

The DNR estimates that there are roughly 52 million woodland ash trees in Iowa and 3.1 million community ash trees. That means a tremendous loss of habitat, loss of canopy, and woodland resource for the state of Iowa.

To replace the ash trees that are lost, Vaughn and Brinkman join in a chorus of saying, “diversify, diversify, diversify.”

Travelling south in Iowa, where the infestation is farther along, it’s easy to see windbreaks of ash trees that were planted to replace windbreaks of elm trees, and now the ash are all dead, according to Brinkman.

When shopping for a new tree, look for a variety. Brinkman notes that Iowa is over-populated with maple trees. For a colorful tree like maple, she says red oak has wonderful color and is one of the faster growing of the oaks.

If people love maples, plant one, but don’t plant all maples, or all of any one species. Diversity will protect the investment when buying a new tree and make for a more interesting landscape.

“The best time to plant a tree was yesterday, the next best time is today,” Brinkman said.


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