The Polar Vortex was a no-show last winter. Hemlock woolly adelgids — the bug that kills hemlock trees — never got iced and returned in strength.
Now, humans have returned to fight off the invaders with a renewed vigor and a swarming mob of black, adelgid-devouring lady beetles.
Thanks to funding from a variety of sources — including the state Department of Energy and Environmental Protection and Steep Rock Preserve in Washington, Conn. — Carole Cheah, a research entomologist with the Connecticut Agricultural Experiment Station’s Valley Laboratory in Windsor, has purchased and released more than 3,800 Sasajiscymnus tsugae beetles throughout the state, including Steep Rock’s Hidden Valley property.
“I saw a resurgence and I thought ‘We have to act,’” Cheah said. “I was saying ‘I’m not waiting. I’m not waiting.”
The beetles feast on the adelgids. Once in place, they multiply and control them for years.
“They’re an effective bio-control,” said Rory Larson, Steep Rock’s conservation and program leader. “They feed on the adelgids from spring through winter.”
In the 1990s Steep Rock saw stands of its beautiful hemlocks decimated by the adelgids. In 1998 and again in 1999, they released 15,500 lady beetles on their property. That — and wintery blasts from the Polar Vortex — kept the invaders in check.
“It’s pretty cool,” Larson said. “Steep Rock was in the forefront with hemlocks.”
Cheah released more beetles at Webb Mountain Park in Monroe in 2017. David Solek, the park’s ranger and Monroe’s tree warden, said the park’s hermlocks look healthy this year.
“I was there a little while ago,” he said. “The needles look very clean. Hopefully, the beetles are doing their job.”
But Solek said all’s not completely well. He’s seen the tell-tale cotton swab nests adelgids build on hemlocks near his home.
The hemlock woolly adelgid is an aphid-like insect native to Asia — China, Japan, India and Nepal.
Somehow, humans brought them to North America. They showed up first in Oregon and British Columbia in the 1920s. In 1951, entomologists identified them in Richmond, Virginia.
The agricultural experiment station, in turn, found them in Connecticut in 1985. Within two years, they’d spread throughout the state.
Adelgids are now found along the Atlantic coast in every county in the 16 states stretching from South Carolina to Maine. They damage hemlocks wherever they go.
They reproduce twice a year, covering their nests with a white, waxy wool-like netting that looks like the end of a miniature cotton swab.
Adelgids have sharp, piercing beaks. They inject those beaks into hemlock branches like a needle and suck the sap out of a tree, especially on young branches. Hemlocks, with their growth retarded, can die off within a few years of being infested.
When state foresters saw the damage the adelgids could do, there was serious concern that Connecticut could lose all its hemlocks.
That would have been an environmental disaster. Hemlocks are considered a foundation species, one that creates and sustains an ecosystem.
They thrive in Connecticut’s acid soils. They’re shade tolerant and can grow on steep slopes. They shade and cool forest brooks and rivers, benefiting fish and aquatic insects. Songbirds shelter in their thick foliage.
However a couple of things worked in the hemlocks’ favor.
One was that sudden, severe cold snaps kill off adelgids. Cheah has documented how the Polar Vortex temperature plunges in recent winters has reduced adelgid populations in the state.
Another is that the experiment station found the bio-control lady beetles in Japan. In 1995, it began releasing them in the state.
By now, Cheah, who has fought a 25-year battle against the adelgids, said the experiment station has released more than 185,000 of the beetles in Connecticut.
They, and the cold, have kept the hemlocks alive.
Cheah credits Tree-Savers, a Pennsylvania-based company, for being the state’s invaluable partner in this work.
Tree-Savers raises the lady beetles for sale. In years when Cheah had no money to buy any, Tree-Savers has donated surplus beetles to her work.
“We recognize the value of our relationships,” said Jayme Boniewicz, Tree-Saver’s director.
Boniewicz said Tree-Savers’ sole product right now is Sasajiscymnus tsugae beetles. During the spring and summer, it sells 3,000 to 5,000 beetles a week.
“Every time we get aspirations to do something else, we get too busy,” she said. “The adelgid has kept us in business.”
And, it’s kept a lot of hemlocks alive. The scourge has been held at bay.
“It’s provided a lot of hope,” she said.
Editor’s note: This article has been updated to indicate a greater number of lady beetles that have been released to combat woolly adelgids.