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It's Winter And The Hunt Is On For Invasive Pests At The Arnold Arboretum06:07
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A painted maple at the Arnold Arboretum. Staff check the tree for Asian longhorn beetle each year. (Robin Lubbock/WBUR)
A painted maple at the Arnold Arboretum. Staff check the tree for Asian longhorn beetle each year. (Robin Lubbock/WBUR)

Through the pandemic, as museums around Boston have opened and closed their doors to visitors, there's one that never had to shut: the Arnold Arboretum.

These days there's plenty of parking along the Arborway in Jamaica Plain, and the Arboretum's wrought iron gate is wide open and welcoming. Even in the dead of winter, this living museum is alive with activity — because the slow season for visitors is the best time to scout for climate threats and alien invaders.

The 281-acre botanical museum, administered by Harvard University, contains about 16,000 trees, woody shrubs and plants. It's "a beautiful green island in an urban sea," says Michael Dosmann, the Arboretum's Keeper of the Living Collections.

But the planet is warming; arboretum scientists say that over the next 80 years the climate is expected to change more than it has in the last 50 million. This means that invading bugs, pathogens and diseases — which are migrating due to climate change — can lay to waste the living museum’s collections. It's the job of Dosmann and his colleagues to protect them.

Arnold Arborteum staff Michael Dosmann and John DelRosso stand by a wood of oaks and maples at the Arboretum. (Robin Lubbock/WBUR)
Arnold Arborteum staff Michael Dosmann and John DelRosso stand by a wood of oaks and maples at the Arboretum. (Robin Lubbock/WBUR)

Dosmann points out one of the Arboretum's treasures: one of the world's richest collections of endangered and rare maple trees.

"Because it's one of our most important collections, we want to make sure that we don't have any pests or pathogens that are going to cause them to go into decline," he says. "We put a lot of extra effort resources into making sure it's happy and healthy."

The job of keeping plants happy and healthy goes to Andrew Gapinski, the Arboretum's head of horticulture.

"Winter is a perfect time to scout for insects and disease," says Gapinski. "All the foliage, flowers and everything else is off the trees. So it really gives you a full picture of every branch, stem and trunk."

Every tree and plant has been mapped using GPS, and it takes the horticulture team five years to rotate through a complete inspection of them all.

"A lot of times it's hard to see by the naked eye, so I typically carry a pruner and a hand lens so that I can take a closer look," says Gapinski, leaning over to inspect a waist-high witch hazel plant. With its tiny orange and red flowers, it's about the only thing blooming in the Arboretum.

Scouting for pests, threats and problems isn’t always so easy. Head arborist John DelRosso sometimes takes a bird’s eye view.

"We get up in the trees with ropes and saddles, and you can get out on most every limb," he says. "Climbing is one of the easiest ways to get around and access as much of the tree is possible. "

John DelRosso, head arborist at the Arnold Arboretum, at work. (Courtesy Arnold Arboretum)
John DelRosso, head arborist at the Arnold Arboretum, at work. (Courtesy Arnold Arboretum)

DelRosso says 2020 was a rough year for the plants, starting with a summer drought that lasted into the fall, followed by windstorms. Then an early snowstorm hit in October, with the leaves still in the trees. "It was a heavy, wet snow. Wasn't a lot, but it was enough. That caused a lot of damage," he says. "So we've been very busy."

Climate change can lead to more extreme weather, which stresses trees and leaves them vulnerable to invaders.

"What keeps me up at night is really the unknown," says Gapinski. When scouting the Arboretum for potential threats, he says he looks for clues in the trees, like branches that are somewhere between alive and dead. "It signals to us that something is happening in that branch," he says.

Andrew Gapinski, head of horticulture at the Arboretum. (Robin Lubbock/WBUR)
Andrew Gapinski, head of horticulture at the Arboretum. (Robin Lubbock/WBUR)

When researchers find something suspicious they cut off the piece of wood, put it into a closed chamber with a vial attached and wait two years.

"All kinds of insects — ants, you name it — emerge, and 99% of them are known," says Gapinski. "But we're looking for that very small amount that might be new to science."

Researchers, using this method, recently discovered a new pest related to the emerald ash borer.

"Many pests and disease have restrictions to where they can go based on temperature," says Gapinski. "As the climate warms, it allows these pests and disease to expand their range. So things that we typically would have found more southern are creeping north and it's a big concern."

In this undated file photo provided by the Minnesota Department of Natural Resources, an adult emerald ash borer is shown. (Minnesota Department of Natural Resources via AP)
In this undated file photo provided by the Minnesota Department of Natural Resources, an adult emerald ash borer is shown. (Minnesota Department of Natural Resources via AP)

The southern pine beetle has been on the march north, and the spotted lanternfly may be heading here, too.

A few years ago, one of these temperature-sensitive exotic pests — the woolly adelgid — threatened the Arboretum’s famous hemlock collection. Gapinski was able to save the tree collection on Hemlock Hill by smothering the bugs with an oily product made from sunflowers.

Protecting this historic living museum — and maintaining a natural balance in a world that is changing — is a constant battle, says Gapinski.

"It’s going to be an ongoing experiment," he says. "But by staying abreast of new information, and working with the research community, there’s a fighting chance."

This segment aired on February 4, 2021.

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Bruce Gellerman Twitter Senior Reporter
Bruce Gellerman is an award-winning journalist and senior correspondent, frequently covering science, business, technology and the environment.

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