January cold likely won’t kill invasive insect
When the January cold came and the state shivered, Carole Cheah cheered.
Really cold weather kills the hemlock woolly adelgid, an insect Cheah has been fighting for decades. The last two winters had been mild and the adelgid — staggered by past polar vortex blasts — made a comeback, again endangering one of Connecticut’s most valuable trees.
So Cheah, a research entomologist with the Connecticut Agricultural Experiment Station Valley
Laboratory in Windsor, welcomed this year’s chill.
“It was finally the weather we needed,” she said.
But we did not get a statewide insect icing.
To truly waste adelgids, the temperature has to fall below zero. That didn’t happen in the middle and southern tiers of the state. Nor was there a sudden plunge going from 40 degrees one day to minus-5 degrees the next.
Gary Lessor, director of The Weather Center at Western Connecticut State University in Danbury, said January averages 26.04 degrees. This January, it was only slightly colder minus–26 degrees.
“It was just ordinary cold,” he said.
But Lessor acknowledged Danbury was atypical this winter.
“We were a warm spot,” he said. “Everyone else was colder.”
Without a true wintry blast, the adelgids — like bad pennies and ABBA tunes — will keep turning up this summer.
“It will be patch by patch,” Cheah said. “In the Northwest Corner, we could see a 50 percent kill rate — maybe higher. In central Connecticut, nothing and along the coastline, nothing. I’m not sure about the Northeast Corner.”
The cold is only one check to the non-native insects. For many years, Cheah has supervised the release of a biological control — Sasajiscymnus tsugae, tiny black lady beetles that feed on hemlock woolly adelgids. Since 1995, she said, more than 200,000 of these beetles have been released in the state.
Because the state seldom funds beetle purchases, Cheah has spread the word to towns, land trusts and private property owners. They, in turn, have bought beetles from Tree Savers, a Pennsylvania company that raises them. The company has donated thousands of the tiny bugs to the state.
In the past few years, Cheah has supervised beetle releases in at the Steep Rock Preserve in Washington, the Platt Farm Preserve in Southbury, and Webb Mountain Park in Monroe
“It has been a wonderful program,” she said.
With the weather being balky, the beetles take on an added importance in combating the adelgids.
Hemlock woolly adelgids — Adelges tsugae — are Asian insects that made their way to the Pacific Northwest in the 1920 and to the East Coast in the 1950s. They’re now found as far north as Nova Scotia.
The agricultural experiment station first identified them in Connecticut in 1986 and they’ve spread to forests in every corner of the state.
Twice a year, female adelgids hatch eggs in a waxy, woolly nest in the underside of hemlock branches. The young hatch, pierce the branches with their sharp beak-like mouths, and feed on hemlock sap. They deprive the tree of its nutrients, and can kill, one in a few years.
En masse and unchecked, they have the potential to snuff out one of the state’s natural treasures.
Hemlocks, called the redwoods of the East, are hugely valuable. They grow tall and can live for hundreds of years. They flourish on steep, thinly soiled slopes along rivers and streams, providing essential shade for cool water-loving aquatic species.
They also provide needed shelter to birds and mammals in winter. More than 90 bird species rely on them for shelter and nesting.
Foresters feared the trees might eventually be lost to the insect invasion. But the trees, helped by icy winter blasts, have proved resilient..
For several years running, a frigid cold air plunged into the state as the polar vortex — the mass of cold air circling the Arctic — broke free and spilled south. By 2019, Cheah had trouble finding adelgids in the state.
Two mild winters in a row gave them respite and the adelgids counterattacked.
“In 2020, I found them in the Northeast Corner and near the Rhode Island border,” Cheah said. “By 2021, they were cropping up in places where they’d never had them.”
This January was, at best, a partial remedy. Nor are there indications of a February big freeze — The Weather Center’s Lessor said longrange forecasts point to a mild February and a warmer-than-average March. There is this caveat. “Long-term forecasts are not always accurate,” Lessor said.