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Crews scramble to map extent of emerald ash borer infestation

  • State foresters Adam Taschereau and Garret Dubois look at possible limbs to sample as they test for the emerald ash borer in East Concord; Wednesday, April 24, 2013. Each spot within a 6-mile radius surveyed has two ash trees sampled, though some spots have no ash trees growing there.<br/><br/>(ALEXANDER COHN / Monitor staff)

    State foresters Adam Taschereau and Garret Dubois look at possible limbs to sample as they test for the emerald ash borer in East Concord; Wednesday, April 24, 2013. Each spot within a 6-mile radius surveyed has two ash trees sampled, though some spots have no ash trees growing there.

    (ALEXANDER COHN / Monitor staff)

  • Galleries made by emerald ash borer larvae are displayed for volunteers to recognize as they peel the bark from scores of test samples taken from ash trees around Concord and surrounding towns; Tuesday, April 23, 2013. The original 1 mile testing grid has been expanded to a six-mile radius and the invasive pest has been found three miles from the original detection site.<br/><br/>(ALEXANDER COHN / Monitor staff)

    Galleries made by emerald ash borer larvae are displayed for volunteers to recognize as they peel the bark from scores of test samples taken from ash trees around Concord and surrounding towns; Tuesday, April 23, 2013. The original 1 mile testing grid has been expanded to a six-mile radius and the invasive pest has been found three miles from the original detection site.

    (ALEXANDER COHN / Monitor staff)

  • Wendy Weisiger, a forester with the Society for the Protection of New Hampshire Forests, checks the location of a sample that tested positive for infestation by the emerald ash borer; Tuesday, April 23, 2013. The sample, one of two that Weisiger cut the day before, was taken from near the Merrimack river, just north of Horseshoe pond. The original 1 mile testing grid has been expanded to a six-mile radius and the invasive pest has been found three miles from the original detection site. <br/><br/>(ALEXANDER COHN / Monitor staff)

    Wendy Weisiger, a forester with the Society for the Protection of New Hampshire Forests, checks the location of a sample that tested positive for infestation by the emerald ash borer; Tuesday, April 23, 2013. The sample, one of two that Weisiger cut the day before, was taken from near the Merrimack river, just north of Horseshoe pond. The original 1 mile testing grid has been expanded to a six-mile radius and the invasive pest has been found three miles from the original detection site.

    (ALEXANDER COHN / Monitor staff)

  • Adam Taschereau of the New Hampshire Division of Forests and Lands watches as an ash tree falls so that it can be tested for the emerald ash borer; Wednesday, April 24, 2013. The invasive pest has been detected in Concord and Bow, making New Hampshire the 19th state to be effected.<br/><br/>(ALEXANDER COHN / Monitor staff)

    Adam Taschereau of the New Hampshire Division of Forests and Lands watches as an ash tree falls so that it can be tested for the emerald ash borer; Wednesday, April 24, 2013. The invasive pest has been detected in Concord and Bow, making New Hampshire the 19th state to be effected.

    (ALEXANDER COHN / Monitor staff)

  • Adam Taschereau (left) and Garret Dubois of the New Hampshire Division of Forests and Lands carry out ash branches to test for the emerald ash borer from a spot in East Concord; Wednesday, April 24, 2013. The invasive pest has been found in several sites in Concord, mostly along the Merrimack river, and in Bow.<br/><br/>(ALEXANDER COHN / Monitor staff)

    Adam Taschereau (left) and Garret Dubois of the New Hampshire Division of Forests and Lands carry out ash branches to test for the emerald ash borer from a spot in East Concord; Wednesday, April 24, 2013. The invasive pest has been found in several sites in Concord, mostly along the Merrimack river, and in Bow.

    (ALEXANDER COHN / Monitor staff)

  • Limbs from ash trees to be tested for the presence of emerald ash borer lay stacked in a Concord warehouse; Tuesday, April 23, 2013. Scores of workers and volunteers from agencies across the state and New England pitched in to detect the spread of the emerald ash borer in and around Concord. The original 1 mile testing grid was expanded to a six-mile radius and the invasive pest has been found three miles from the original detection site.<br/><br/>(ALEXANDER COHN / Monitor staff)

    Limbs from ash trees to be tested for the presence of emerald ash borer lay stacked in a Concord warehouse; Tuesday, April 23, 2013. Scores of workers and volunteers from agencies across the state and New England pitched in to detect the spread of the emerald ash borer in and around Concord. The original 1 mile testing grid was expanded to a six-mile radius and the invasive pest has been found three miles from the original detection site.

    (ALEXANDER COHN / Monitor staff)

  • State foresters Adam Taschereau and Garret Dubois look at possible limbs to sample as they test for the emerald ash borer in East Concord; Wednesday, April 24, 2013. Each spot within a 6-mile radius surveyed has two ash trees sampled, though some spots have no ash trees growing there.<br/><br/>(ALEXANDER COHN / Monitor staff)
  • Galleries made by emerald ash borer larvae are displayed for volunteers to recognize as they peel the bark from scores of test samples taken from ash trees around Concord and surrounding towns; Tuesday, April 23, 2013. The original 1 mile testing grid has been expanded to a six-mile radius and the invasive pest has been found three miles from the original detection site.<br/><br/>(ALEXANDER COHN / Monitor staff)
  • Wendy Weisiger, a forester with the Society for the Protection of New Hampshire Forests, checks the location of a sample that tested positive for infestation by the emerald ash borer; Tuesday, April 23, 2013. The sample, one of two that Weisiger cut the day before, was taken from near the Merrimack river, just north of Horseshoe pond. The original 1 mile testing grid has been expanded to a six-mile radius and the invasive pest has been found three miles from the original detection site. <br/><br/>(ALEXANDER COHN / Monitor staff)
  • Adam Taschereau of the New Hampshire Division of Forests and Lands watches as an ash tree falls so that it can be tested for the emerald ash borer; Wednesday, April 24, 2013. The invasive pest has been detected in Concord and Bow, making New Hampshire the 19th state to be effected.<br/><br/>(ALEXANDER COHN / Monitor staff)
  • Adam Taschereau (left) and Garret Dubois of the New Hampshire Division of Forests and Lands carry out ash branches to test for the emerald ash borer from a spot in East Concord; Wednesday, April 24, 2013. The invasive pest has been found in several sites in Concord, mostly along the Merrimack river, and in Bow.<br/><br/>(ALEXANDER COHN / Monitor staff)
  • Limbs from ash trees to be tested for the presence of emerald ash borer lay stacked in a Concord warehouse; Tuesday, April 23, 2013. Scores of workers and volunteers from agencies across the state and New England pitched in to detect the spread of the emerald ash borer in and around Concord. The original 1 mile testing grid was expanded to a six-mile radius and the invasive pest has been found three miles from the original detection site.<br/><br/>(ALEXANDER COHN / Monitor staff)

At the edge of a quiet grove in north Concord, the shriek of a chain saw sends a leafless giant swaying in the daylight.

Two men, one with a hardhat, the other a clipboard, step back and watch as a massive ash tree cracks and tumbles to the ground.

Another one down.

For weeks now, this scene has played out dozens of times around this city, which has fallen victim to the most destructive invasive species known to have ever hit American forests.

As state and federal authorities hammer out a strategy to combat the spread of the emerald ash borer, a small Asian beetle that has felled tens of millions of trees nationwide and was discovered in Concord for the first time last month, local officials are now scrambling to map the extent of the infestation in Merrimack County.

The alarm is high because the sighting was the first in state, and it could portend havoc for the more than 25 million ash trees that populate its northern forests and urban areas. It could also have a significant financial impact on the state’s timber industry.

And this isn’t the first major outbreak to hit the state’s forests: The chestnut population was hit by blight in the 1930s, and elm trees that once lined city streets were removed decades ago because of disease.

Officials have long feared and planned for an ash borer outbreak, and since verifying the discovery have responded with speed.

Agencies including the Department of Resources and Economic Development, the Division of Forests and Lands, and the U.S. Department of Agriculture are working together to pinpoint infested trees in and around Concord.

Knowing the density and location of the borer population will help experts determine the most effective means to blunt its spread.

“Our goal, really, is only to slow this thing down long enough so that our ash isn’t all gone by the time bio(logical) controls take off,” said Kyle Lombard, a forest entomologist with the Division of Forests and Lands, who is overseeing the day-to-day survey operation.

Small sampling

State and local officials have divided the city into quarter-mile quadrants and are sampling two suspect trees from each. They’re also removing samples from dozens of grid points within a six-mile radius of the first detected tree, or “mother tree,” on Hall Street in south Concord.

Staff from various departments and local organizations, such as the Society for the Protection of New Hampshire Forests, as well as foresters from neighboring states, have pitched in to assist with the survey.

The process starts with survey teams combing each quadrant, marking suspect trees and contacting landowners for permission to remove samples. Pairs of certified tree cutters are then dispatched to remove three meter-long sections of each marked tree. Depending on its size, samples, or “bolts,” are removed by either pruning or felling the entire tree.

Bolts are brought to a rusty state transportation department warehouse near downtown, which has served as a makeshift headquarters for Lombard and his staff. The bolts are checked for visible signs of the pest, which include snaking paths where larvae have tunneled into the wood called “galleries,” D-shaped exit marks and bark removal where woodpeckers have tried to reach the borer larvae.

Ash trees often die within five years of infestation. Borer larvae tunnel under the bark, cutting off the supply of nutrients to the tree. If left unchecked, experts say the beetle could wipe out ash trees in New Hampshire within 10 years.

So far, only a handful of trees have tested positive for signs of the beetle, but Lombard believes the infestation is far more substantial.

“There are thousands of trees infested in this area,” he said. “It’s just that we’re only sampling a very small number of them.”

The infestation appears to be concentrated along the Merrimack River. That’s where most of the infested trees have been detected to date, and that’s where the air currents and most of the ash is located, according to Lombard.

Beyond that, though, there doesn’t seem to be a pattern. Crews have found evidence of the pest in quadrants neighboring others that have shown none.

“It’s very spotty, which is good,” Lombard said. “It means we caught it early.”

Typically, when the beetle is introduced to a region, its population grows steadily for the first four years and then explodes in year five. Based on the survey so far, the insect appears to have been in Concord for just three or four years, Lombard said.

That could mean there’s still time to slow the spread.

“The bottleneck right now is we’ve got a stack of places to sample but haven’t gotten permission yet,” Lombard said. “No one has said no, really, but it’s just that they take time in responding to the fliers we put in their doors.”

Lombard said last week that crews had sampled half of the mapped sites and would likely complete the survey sometime this week, which is significant since borer larvae begin to emerge and take flight in late May.

“What we’re really asking people in this area to do is be kind to us when we ask to sample their trees,” he said. “And if they have a tree they’d like us to sample, we’d be more than happy to come out.”

The beetle was probably transported to New Hampshire via firewood from one of the 18 other infested states. Though authorities have banned the import of out-of-state firewood since 2011, the age of the infestations discovered already suggests the first specimen was hauled in well before that took effect.

Concord was a likely spot for the first sighting, Lombard said, because it has a relatively dense ash population and it’s a hub for campers and other visitors.

“You want to get to the North Country, you want to get to the Seacoast, you want to get to the racetrack, the mountains, you’ve got to come through Concord,” he said.

State officials have been tracking the beetle nationally for years. In 2006, they began surveying campsites across the state to determine how much firewood was coming from other states (42 percent, according to Lombard). Since then, officials from the Division of Forests and Lands have responded to hundreds of possible borer sightings.

“We’ve done 450 of these in the last 10 years, of people calling and saying they have a symptomatic tree, and 439 of them came up negative,” Lombard said. “It was the 440th that came up positive. That’s why you just can’t ever blow anyone off. You just never know if it’s going to be that one.”

Two options

With the end of a 30-day emergency quarantine on ash products approaching, it’s unclear yet what longer-term regulation will be. The state is holding two public hearings in Concord this week to provide information and get feedback from the public about what it knows and how it plans to manage the beetle.

Lombard said he suspects the local quarantine will remain in place indefinitely, though there may be exceptions to the restriction – as there are now – for trees that are ground to a certain size.

Long term, though, the choices will be limited.

For residents with infested trees, there are essentially two options, and neither is ideal, or cheap: remove them or treat them with pesticides.

The problem with pesticides – perhaps one of several problems – is that older trees typically do not absorb less heavy chemicals administered through the ground. Such trees often require a stronger variant that is expensive and must be applied directly into the trunk by a certified professional, a more expensive and labor-intensive process.

“It can be effective for the occasional legacy tree, but it’s not a solution for the forest.” Lombard said.

A strategy that has worked to some extent in other states is creating decoy, or “sink” trees – essentially standing, decaying trees – which attract the beetle. The trees are removed once they have become saturated with the insect.

The other option is natural predators, such as parasitic wasps and woodpeckers. But scientists are still researching the viability and effectiveness of certain foreign wasp species, and it could be years before there is a successful biological control to the infestation. No other state has successfully eradicated the beetle so far.

Back in the woods in Concord, Garret Dubois, the man with the clipboard, walks down an old dirt road that has been overtaken by trees. Brush cracks under his boots as he stares up, scanning for signs of the beetle. Though he doesn’t spot any, he and his colleague, Adam Taschereau, both forest technicians with the Division of Forests and Lands, must still take a sample, which in this case could mean killing a perfectly healthy tree.

He can’t seem to decide on an ash to cut.

“I hate signing the death warrant on any one of them,” he said.

(Jeremy Blackman can be reached at 369-3319, jblackman@cmonitor.com or on Twitter @JBlackmanCM.)

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