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The emerald ash borer can't be stopped, but it's blow can be softened

It may be next year or three years from now, but one thing is certain: The emerald ash borer, which jumped from eastern Wisconsin to western Minnesota in one year, is coming to North Dakota. It might even be here now, according to Jeff Hahn, an e...

It may be next year or three years from now, but one thing is certain: The emerald ash borer, which jumped from eastern Wisconsin to western Minnesota in one year, is coming to North Dakota. It might even be here now, according to Jeff Hahn, an extension professor in entomology for the University of Minnesota in St. Paul, where in May the emerald ash borer first was discovered in the state.

"In the cases where states have found it for the first time, when they really look closely at those sites, they discover it's been there at least five-plus years," he says.

One bad bug

The emerald ash borer, now commonly referred to as EAB, came to the U.S. in 2002 from eastern Asia. There, the inch-long metallic green beetle is regarded as more of a nuisance pest, like the poplar borers and bronze birch borers found in the Upper Midwest, which only cull weak and dying trees.

But EAB has become much more than a nuisance in North America.

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"EAB is a highly destructive insect," Hahn says. "When it gets to an area, it very systematically attacks all the ash trees, regardless of species, size or state of health, and eventually kills them."

It landed in the U.S., probably in the wood of shipping crates from Asia, at Detroit, Mich., and began to spread. But because EAB does its damage while under the trees' bark, it was not noticed for some time.

"It's difficult to detect them in the trees when they first are infesting them, and it takes several years before you start seeing dead tress in a particular or a new area," he says.

So by the time Tim Wilson, the public works director for the Detroit suburb of Westland, discovered it in 2002, it was too late. Westland was to become one of the first casualties of EAB.

"By 2004, there was not a single ash tree within our community," he says in a report. "We literally could not keep up with the pace of the insect's destruction."

EAB has since gone on to kill millions of ash trees, spreading in every direction from Detroit. It only flies about one mile each year, but tree and wood transportation have provided the hitchhiking bug a very effective mode of spreading. In the seven years since Westland began and lost its battle, the insect has spread to a dozen northern U.S. states and to Quebec and Ontario in Canada.

Efforts to control spread have been futile, despite millions of U.S. Department of Agriculture dollars being spent on research. The emerald ash borer goes to wherever it can catch a ride, leaving dead trees and expensive cleanup and replacement efforts in its wake.

Once infested, only yearly chemical applications can extend an ash tree's life. And considering its one-year leap from Milwaukee, Wis., to St. Paul, forestry specialists in North Dakota are now bracing themselves for attacks on the ash trees in state parks, along city boulevards and among the thousands of miles of shelterbelts that line the state's farmlands.

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At stake

North Dakota has some 47 million ash trees, mostly green ash, which replaced the majority of the American elms when they fell to Dutch elm disease. The green ash make up about 90 percent of the total canopy in some woodland areas and are valued at $3.5 billion.

According to Michael Kangas, a forest health specialist with North Dakota Forestry Service, rural landowners are going to be facing "significant impact."

"Ash was probably one of the most common tall deciduous species used in rural plantings in North Dakota and the Northern Plains," he says. "Unfortunately, all of those trees are going to be at risk for emerald ash borer when it gets to North Dakota."

He notes other areas at risk, including wooded draws in the western part of the state, where cattle gather for protection from harsh weather conditions.

"Ash is also a pretty important species for wildlife, not only for seeds for food, but also from the standpoint of cover," he says.

The extensive use of ash in riparian projects also may put water quality and wildlife habitats at risk, he says.

As for the ash trees in use on North Dakota farm and ranch properties, Kangas recommends that farmers take inventory of their individual situations.

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"I think what farmers need to consider is, when they look at either their field windbreaks or maybe they have a living snow fence around their property, they need to make an assessment as to how much ash is in there, and what purpose it serves," he says.

Transition game

If ash trees make up a significant portion of their woodlands, he says farmers should consider taking action ahead of time by planting other species of trees in areas that would be left open by an EAB infestation.

"If you get them established now, it might be a little easier than waiting for EAB to get here and then having to contend with removing all those trees and replanting," Kangas says.

He recommends speaking with forestry or tree specialists to discern the best replacements for a given area and offers a few options to consider. Among those is the basswood, which is a very shade-tolerant tree.

"But basswood is not very drought tolerant, so you have to have good soils or be able to supplemental-water them," he says. He and a neighbor are planting basswood under ash trees near the Red River, so as the ash die off, the basswood will be there to fill the void. He also recommends willow trees in wetter areas.

For the western portion of the state, a number of trees are available. Some conifers such as the Rocky Mountain juniper or Ponderosa pine are good replacements for shelterbelts, he says.

"They're very cold-hardy and drought tolerant, which is very important," he says.

Young hackberry can be difficult to get established because deer like to nibble the leaves, but it does have moderate drought tolerance. Bur oak is also very cold-hardy and very drought tolerant, though again, deer may hamper their growth, Kangas says.

If a windbreak or shelterbelt already is overgrown with multiple species of wild trees, there may be less to worry about.

"What you often see in your windbreaks that become overgrown, is that sometimes it's a good thing, because (other trees) will seed in naturally," he says. "There are things like box elder, which we don't consider a valuable tree, but if you want a windbreak and you want to have some regeneration in there, it's not necessarily a bad thing to have."

Planning ahead can alleviate heavy, immediate short-term expense later on, he says. Beginning a transition effort now is better than dealing with an EAB attack that can leave major gaps in shelterbelts and living snow fences.

Whether it's already in North Dakota, no one knows. But thus far, emerald ash borer has not been stopped.

"We recognize that we can't eradicate EAB," Hahn says. "We would be extremely lucky, and no one's holding their breath here in St. Paul. And if it's been here for five-plus years, who knows how many opportunities it has had to spread?"

Information: www.emeraldashborer.info .

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