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Treat the tree? No-cut solution available for ash borer

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Frank Schultz
April 5, 2013

— Now that Janesville is a ground zero for the destructive emerald ash borer, owners of ash trees have wondered when they'll have to cut them down.

They may not need to.

That's the message from Phyliss Williams of K&W Greenery, one of the stores that sells do-it-yourself insecticide formulated to fight the tree-killing beetles.

"The nice thing about the emerald ash borer is that we can stop it," said Williams, who is offering free classes for do-it-yourselfers Saturday.

Spring is the ideal time to treat ash trees, but research shows fall also is effective, according to the UW-Madison emerald ash borer website.

Trees should not be treated when the ground is frozen or waterlogged, Williams said.

The UW-Madison website says treatment is "most appropriate" in counties quarantined for emerald ash borer or within 15 miles of a known infestation.

Rock and Walworth counties are under quarantine, and infestations include Janesville, Clinton and the Lake Geneva and Mukwonago areas.

Large numbers of trees have not yet died,here, but don't let that fool you.

"It can happen so fast," said Williams, who comes from Michigan, where large sections have lost all their ash trees.

Williams visited Michigan last year and was shocked at how whole neighborhoods she knew were unrecognizable.

"The trees are just gone. It changes everything," she said.

The treatments are not just for sick trees. In fact, they work best on healthy trees, according to the UW website. Treatments might be too late for stressed or injured trees.

Williams said the treatments are guaranteed to work.

Dan Herms, a leading specialist on the borer at Ohio State University, agreed insecticide treatments are effective.

Treatments can be economical when the cost of cutting down the tree is considered along with a tree's environmental and aesthetic value, Herms said.

Herms said not every tree is worth saving, but he advises owners to consider treating those that are.

Treating a tree is simple. It involves mixing the product in water and drenching the soil around the base of the tree.

The product's main ingredient is called imidacloprid, which is used to battle a wide range of insects. Williams said the Bayer product has been changed in the last year. It now is effective on caterpillars because tent caterpillars can be a problem.

Cost depends on the tree's circumference: 1 ounce of product for each inch of circumference, measured at shoulder height, Williams said.

A 32-ounce bottle of the product costs $24.99, although Williams said she'll be offering discounts Saturday.

That bottle could treat a tree of 16 inches in circumference for two years. But having a tree removed could cost upwards of $1,000, Williams said.

Another consideration is that removing a tree can increase air-conditioning costs.

Williams said home applications are not as effective on very large trees. In those cases, commercial applications—in which the treatment is injected into the tree trunk—are available from tree services, foresters and others who are licensed applicators, including K&W.

Emerald ash borers attack only ash trees, so owners of small ash trees might consider replacing them with non-ashes, but Williams cautioned that might not work.

Other invasive insects, such as the Asian longhorned beetle, which can kill maples and other hardwoods, has established itself in parts of the United States, Williams noted. Other pests or diseases could attack the tree that replaced the ash tree.

"It does make you wonder what the forest will look like in the future," Herms said. "I'm sure these (pests) aren't the last."

Scientists don't yet know what the borer will do after it has been in an area for many years and after most ash trees are gone.

Researchers are studying whether trees too young to produce seeds will survive or whether the ash borer will kill them as they get big enough.

"Right now, it looks like they'll just pick them off," Herms said.

As ash borer numbers decline, research indicates owners might be able to decrease insecticide treatments, making them more viable.

"It took about seven years of intense treatments, and now we're to the point we can start dialing back," Herms said.

Researchers are experimenting with biological controls to combat the insect.

Herms predicted the insect would behave like chestnut blight, which sticks around in low levels and leaves a few healthy trees.

Gazette reporter Marcia Nelesen contributed to this report.



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