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Vermont Undertakes a Methodical Search for a Forest Pest

  • FILE- In this undated file photo provided by the Minnesota Department of Natural Resources, an adult emerald ash borer is shown. Millions of tiny wasps as small as a grain of rice have been released into wooded areas in 23 states as the battle against the emerald ash borer turns biological. The U.S. Department of Agriculture has researched and approved for release in the U.S. four species of parasitic wasps that naturally target the larval and egg stages of the ash borer. (Minnesota Department of Natural Resources via AP, File)



VtDigger
Sunday, March 25, 2018

The search keeps widening in scope, from an isolated woodlot into the adjacent forests, from Orange County into Caledonia and Washington counties.

“We have some suspects that we’re following up on,” Barbara Schultz, Forest Health Program manager for Vermont’s Department of Forests, Parks and Recreation, said in a recent interview. She laughed, ruefully, when it was suggested that this sounded like a manhunt.

“It is a little like that,” she said. A beetle-hunt.

The suspect in question is the emerald ash borer, a green buprestid, or jewel, beetle, from the temperate regions of Asia — China, Mongolia, the Korean Peninsula.

For a few weeks in the late spring and summer, its description would be something like “bright metallic green, about a third of an inch long.” But it is in its larval stages that the beetle does its damage, eating its way through the inner bark of ash trees, cutting the tree’s lifelines, blocking water and nutrients. Trees infested by the borer are usually dead in three to five years.

The ash borer (Agrilus planipennis) was first found in the United States in Michigan in 2002 — though it is believed to have been around for a decade before that. It has been devastating the ash groves of North America ever since. Tens of millions of ash trees have succumbed. In February, Vermont joined 31 other states, and several Canadian provinces, with emerald ash borer infestations.

The search underway in central Vermont is a “delineation survey,” the first step in the state’s “action plan” for dealing with the borer. Vermont’s plan has been in place for years, because the beetle’s arrival has been seen as inevitable. New York state, the surrounding New England states, and the province of Quebec all have infestations.

At a public meeting in Barre this month, state and federal forestry and agriculture officials said the delineation survey will answer the question that has been on many minds since a consulting forester first spotted a dying ash tree in a remote woodlot: How bad is it?

“That’s our first question,” Schultz said. “What does this infestation look like? Is it just a few properties, or is it over a wider area?”

Signs so far are not encouraging. The evidence indicates the beetle has been around awhile, Schultz said, and it is not isolated to Orange County. “That much is clear from the condition of some of the trees,” she said. “The infestation has been here several years.”

“That’s how it goes with emerald ash borer infestations,” she said. “It generally takes several years before an infestation is detectable.”

The beetle operates under the cover of the tree’s bark, and the initial damage is usually near the base of the tree’s crown — too high to be easily noticed. The first sign of trouble often is the appearance of woodpeckers in unusual numbers, and by the time they’ve arrived, it’s too late.

The survey is being conducted on a grid system — every square representing a square mile of land — and it will be largely a matter of following the damage.

The ash tree is ubiquitous in northern hardwood forests — around 5 percent of Vermont’s trees are ash. It is an especially valuable tree, used in construction and cabinetry and for everything from shovel handles to baseball bats to wooden spoons.

How long it will take to complete the initial assessment will depend in part on the results, Shultz said. Evidence of the beetle in one town will trigger a new search in adjacent towns. The more evidence of infestation, the wider the search. The goal is to have the survey finished, and the quarantine decisions made, by May 1, she said.

The second phase of the plan, a quarantine, is intended to isolate the infestation as much as possible, Schultz said, to help slow the spread, and to buy time.

Even when a quarantine is in place, ash trees can be harvested and processed — at certain times of year, under certain conditions — specifically during the “nonflight” season in the cold months. As conditions warm, in late May and into the summer months, the beetles emerge. Females live for about six weeks, and usually lay around 60 to 80 eggs, though some can lay as many as 200.

“Quarantine is a hurdle,” Schultz said, not a blanket ban. “Quarantine doesn’t mean you’ll never sell another ash log.”

The state also plans to explore methods of combating the beetle. There is the biological approach, which involves attempting to establish a local population of the small Asian wasp species that is the beetles’ only predator. New Hampshire and Massachusetts, among other states, have already done so, with mixed results.

“They’ve been widely introduced, and appear to be having an impact on the levels of emerald ash borer,” Schultz said.

There is also the chemical approach: insecticides. Some have proven effective but the treatment helps only healthy trees, and the insecticides require reapplication every few years. It’s a valid approach for so-called high value trees, in landscapes and in city parks, but not a practical solution in a forestry environment, Schultz said. There are simply too many trees. At the moment there is no sure way to control the emerald ash borer in forests.

One of the uses of the insecticides would be to maintain a population of ash trees that live long enough to produce seeds — 10 years — “to help the next generation get started,” Schultz said. “The next generation is our glimmer of hope in terms of perpetuating the ash tree.”

Because while the emerald ash borer is a pretty thorough tree killer, she said, it’s not necessarily 100 percent. “If it’s 99 percent fatal, that means there is still 1 percent still standing. And that is a lot of ash trees.”

When the beetle appeared in Michigan, almost nothing was known about it. It hadn’t even been studied in its native habitat.

“People said at the time that what was known about the emerald ash borer would fit on a page,” Schultz said.

“There was a lot to learn,” she added. “Just six years after that, it was found in Montreal. Ten years after that, we know a lot about the emerald ash borer, and we’ll know even more five years from now. The longer we can keep this insect from spreading, the more opportunities we’ll have to address it, with the best knowledge we have.”