As emerald ash borer broadens its base in Vermont, other alien insects lurk
This road is made for walking, inclining gently upward, not too muddy. A mountain stream rushes alongside, noisy with snowmelt. In summer it is cool, shaded by a mix of trees commonly found in the forests of northern Vermont — a scattering of hemlock, cedar in the low-lying areas, but mostly mixed hardwoods, birch, sugar maple, ash.
So many ash trees, rising tall and straight toward gaps in the tree cover.
Given the news last week, that evidence of the invasive emerald ash borer now has been found in four towns and three counties in northern Vermont, the ash lining this road merit closer examination.
Those patchy places on the trunk 15 feet up, where the bark is pale and scaly: Is that just ordinary wear and tear on an aging tree? Or is it “blonding” — the term foresters use for evidence of damage by beetle larvae? Is that a hole in the bark, or is it a D-shaped hole in the bark, the telltale sign that an adult beetle has exited?
The road is in Peacham, by Groton, which is one of the towns now identified as being inside the perimeter of the emerald ash borer infestation zone, along with Barre, Plainfield and Orange. Peacham is in Caledonia County, the second most forested county in the state, and one of the three counties now identified as infested.
In the 16 years since it was found in Michigan, having traveled, probably by wood pallet, from temperate east Asia, Agrilus planipennis has been responsible for the deaths of millions of ash trees across North America. The wood-boring beetle takes no prisoners.
As the delineation survey enters its fourth week — an “all hands on deck effort” involving the state Agency of Agriculture, Food and Markets, the Department of Forests, Parks and Recreation, the U.S. Forest Service, the USDA’s Animal and Plant Health Inspection Service, the University of Vermont and others — it is still too soon to tell where it will end, Vermont state forester Steven Sinclair said in a recent interview.
Two crews, of two or three members, set out daily from Berlin — the agriculture agency laboratory there is emerald ash borer command central — to drive the roads of northeastern Vermont with binoculars, looking for signs and symptoms of trouble. Suspect trees are photographed, GPS coordinates recorded, samples taken, and sent to APHIS, a division of the USDA.
Once the extent of the infestation has been determined, and its perimeter demarcated, then attention will turn to how to contain it. That there will be a quarantine is a given. The question is whether it will be statewide, or county by county.
A ‘trifecta’ of invasive insects
But the emerald ash borer is only one of what Sinclair last week referred to as “the trifecta” — “the three major invasive species we need to be concerned about in Vermont.”
Another species of concern in Vermont is the hemlock woolly adelgid, Adelges tsugaea, a tiny aphid-like invasive insect that, as its name implies, kills hemlock trees — hemlock is the third most common tree species in Vermont. The adelgid has been identified in Windham County and to a lesser extent in Windsor and Bennington counties.
The third and — potentially — scariest of the three, is the Asian longhorned beetle. Another accidental import from east Asia, it is about an inch and a half long, glossy black with random white spots — it is also known as the starry sky beetle. It has a pair of sporty black and white striped antennae, and an appetite.
The USDA’s Animal and Plant Health Inspection Service doesn’t mince words in its warnings about Anoplophora glabripennis. “The ALB has the potential to cause more damage than Dutch elm disease, chestnut blight and gypsy moths combined, destroying millions of acres of America’s treasured hardwoods, including national forests and backyard trees. … It threatens recreation and forest resources valued at billions of dollars.”
For Vermont, in particular, the prospect of an alien invasion by the Asian longhorned beetle has horror-movie undertones. It is not because the larvae eat trees from the inside out, or that they feed on 13 species of hardwoods — all of which can be found in state’s hardwood forests.
It is that their preferred species are maple: Norway, red and sugar.
The scenario this conjures — the possible cost to the state’s economy, the mega-million dollar maple industry, tourism, the very image of Vermont — imagine an autumn color palette minus all the reds — is incalculable and unimaginable, so most people prefer not to.
“The potential impact on Vermont — the loss of maple. It would be … ” Meredith Whitney, the UVM extension service’s forest pest education coordinator, pauses to search for the right word. “Horrible.”
Fortunately, while the Asian longhorned beetle has proved to be a mass destroyer where it lives, it isn’t much of a traveler. Following its arrival in the U.S. — in Brooklyn, in 1996 — it has been found only in New York, Ohio, and Massachusetts.
When the beetle turned up in 2008 in Worcester, Massachusetts, a city of about 200,000 in east central Massachusetts, there was sleep lost in Vermont.
Because the Asian longhorned beetle is regarded as a national priority pest, efforts to contain and control it have been managed by the USDA. And a solution was identified that was effective, and costly.
It was found that the beetles could be, literally, starved out. It required removing and destroying not only infested trees but also all of the trees surrounding them — in a radius wide enough that there was nowhere for the beetles to go, and more importantly nothing to eat.
So far a total of 35,000 trees have been cut down, in Worcester and a few surrounding communities — a quarantine zone of 110 square miles. About half of the trees were infested; the rest were the so-called host trees. It worked: The number of trees found to be infested fell from a high of nearly 12,000 the year after the beetle was found, to only 94 in 2016. The beetle for now is in a holding pattern.
“Can you imagine in Vermont if we had an infestation of Asian longhorned beetle and we had to remove every maple tree in the vicinity of an infected tree, within a quarter mile radius? What an impact that would have on a sugar bush?” Sinclair said.
“We really owe a debt of gratitude to the state of Massachusetts and to the city of Worcester and to APHIS for their valiant efforts to contain it,” he said. “They’ve not eradicated it, but they have contained it.”
In fact, such was the gratitude of Vermonters — foresters, forestry product industry reps, and especially maple producers — that they threw a pancake breakfast for everyone involved in the Massachusetts campaign to contain the Asian longhorned beetle. It was in December 2016, at Worcester Technical High School, complete with maple syrup and certificates of appreciation.
Whether Worcester will be the beetle’s Waterloo remains to be seen. As far as the extension service is concerned it remains on the most-wanted list, with its other partners in crime Coleoptera. There are posters, and postcards, containing the likenesses and descriptions of the insects, which are in wide distribution at fairs and campgrounds.
There is an ongoing statewide campaign not to move firewood — Burn it where you buy it, is the motto — because firewood has proved to be the main mode of transport for invasives.
Compared to the glossy black and white Asian longhorned beetle, and the emerald ash borer, which as an adult is a brilliant metallic green, the hemlock woolly adelgid is as tiny as it is nondescript. The smallest of the trifecta, it hides out in white “woolly” masses of wax, about half the size of a cotton swab, that females produce in late winter and attach to the base of hemlock needles. But it is hardly harmless.
The adelgid arrived in the U.S. in Richmond, Virginia, in the 1950s, from Japan. An insect with a complex life cycle, it was kept in check in its native habitat by a combination of tree hardiness and predatory insects.
It has not spread in Vermont as far or as fast as initially feared — nor has it wreaked the havoc it has in the Appalachian region where it has laid waste to vast tracts of hemlock forest — because of an apparent cold intolerance.
“In years of really cold winters, as we’ve had this year, the population level drops dramatically,” Sinclair said. “It builds itself back up, but what we’re seeming to find is the spread has been slow compared to other states. We’re also seeing much less mortality in trees.”
Work is being done on introducing other insects known to be adelgid predators, including a ladybug and a species of wasp. But it is a race against time and the trend toward warming winters resulting from climate change.
Of the three in the insect trifecta, the emerald ash borer is probably “the worst,” in the opinion of to those who study them. It remains the one without any natural predator, or proven means of control in a forest environment.
However, just because an insect is yet to be proven ineradicable, doesn’t mean it can’t be contained, Nate Siegert, a forest entomologist with the USDA and an authority on the emerald ash borer, said last week.
“There’s a wide range of management across the U.S. right now,” Siegert said. “Usually we don’t try to eradicate the insect, we try to mitigate the impact, slow the rate of ash mortality in an area with a number of different tactics and tools. Those will be part of our recommendation, once we find out how big this is.”
Ash trees are city assets, too
While much of the attention has been on Vermont forests and its forest products industries, the loss of the ash tree is is no small matter to municipalities.
“The fact is the emerald ash borer will eat any ash tree, whether it is in a forested setting or along a city sidewalk,” Sinclair said. The borer’s impact on Vermont’s cities and towns could be “very devastating” he said.
The division of forests and the UVM Extension Service both have been working with Vermont communities to develop emerald ash borer response plans. Thirty cities and towns have plans in place.
Sinclair has cited as one example the town of Randolph, which has calculated that it would cost $300,000 to remove and replace the ash trees along public rights of way within the town.
In Stowe, he said, 50 percent of the trees are ash. In Rutland it is 17 percent. The town of Williston, where 42 percent of the trees are ash, is already making plans to replace them.
It’s no small irony that ash trees were planted in parts of the U.S. to replace the American elm following the devastation of Dutch elm disease in the 1970s.
Urban arborists called them “bulletproof,” Sinclair said. “They grow well in urban settings, where there’s not a lot of room to grow, in areas of compacted soils. They’re tolerant of salt. And they didn’t have a lot of insect and disease problems … until the emerald ash borer came along.”
Vermonters who make their living in or from the forests are understandably anxious to know what is going to happen next. There is no place for complacency in this calculus.
“We knew it was only a matter of time before it would come to Vermont. Now that it’s here it’s important to recognize that it poses a genuine threat to the short and long term health of our forests, and thereby to all those who earn their living from forests, loggers, foresters, and the mills, as well as landowners,” said Bill Sayre of Johnson Co., a lumber mill in Bristol, and a member of the Vermont Woodlands Association.
Ash is second only to maple in the number of board feet of hardwoods harvested in Vermont. Both are outstripped by the harvest of softwood species white pine, spruce and balsam, but the importance of ash in forestry cannot be underestimated.
“There was another species of tree about 125 years ago, known as the American chestnut, that started to develop a blight. We didn’t know as much then about containing insects and disease as we do today. The result of that is you hardly hear about an American chestnut any more,” Sayre said. “We don’t want that to happen to the ash tree here in Vermont.”
At a press conference in Randolph last week, Rep. Peter Welch, D-Vt., announced a number of measures he would pursue, saying “we are determined to do everything we can do to mitigate the threat the emerald ash borer presents to Vermont forests and industry.”
They included requesting a funding increase to $60 million for the USDA’s Tree and Wood Pest program. Vermont Sen. Patrick Leahy, D, had recently gotten the funding increased to $56 million. Welch also said he would introduce legislation creating a grant program to fund research focused on protecting native species.
Welch pledged to work with Vermont’s two senators to build a nationwide coalition of districts that are threatened by the emerald ash borer, to “make sure we do everything we can to support the research.”
“We can’t let our guard down,” he said. “This is too important to our forest industry in Vermont, and not just the forest industry. Ash trees are a major staple of our urban areas.”
“So,” he said, by way of conclusion, “Let’s save our trees.”