A hemlock woolly adelgid-infested branch. Connecticut Agricultural Experiment Station photo
Boothbay Regional Land Trust and Coastal Rivers Land Trust joined forces to introduce Japanese lady beetles to the Midcoast in an effort to combat another pest that poses a threat to nearly 10% of Maine’s trees.
The beetles are meant to target hemlock woolly adelgids. Woolly adelgids deposit their egg sacs on hemlock needles, leaving strings of white that resemble fake snow on a Christmas tree. They drain the sap from the tree, eventually killing them. Lady beetles serve as a natural defense.
“We’re glad to collaborate and serve the Boothbay/Pemaquid peninsula as a whole,” said BRLT communications manager Christine Selman. “Nature knows no bounds, let alone service areas, and it takes a team to address this issue.”
According to Selman, both organizations began conversations in 2022 when they grew concerned about the increasing number of sick hemlock stands. After receiving a grant from the Maine Outdoor Heritage Fund in November, they decided to pool together resources to place a joint order: $5,500 for 20 colonies with 100 beetles each.
In June, thousands of period-sized lady beetles from supplier Tree Savers were placed along a 1-mile stretch at Ovens Mouth Preserve. While it’s still too soon to tell, Selman said, both groups hope to spot improved needle growth — a sign of the projects’ success — come early winter.
“This solution has great potential,” said CRCT stewardship director Brad Weigel. “The willingness of two land trusts to team up is beneficial not only economically but also in terms of education. The more people who know how to identify and treat woolly adelgids, the better. We’ve got a real shot at recovery.”
Identification
Initially found in the southern tip of Maine, the woolly adelgid thrives in warm climates and has spread up the coast, affecting trees as far north as Acadia National Park.
Weigel said a warming climate is likely to worsen the issue. The first step to mitigation is identification, he said, outlining the signs to look for.
When the tree has been infested for a while, it looks sickly — the lower branches die off, the canopy lacks vigor and the bark turns grey. When the infestation is newer, woolly masses can be found on the underside of the branches where the needles start.
Tree Savers lady beetles come in a container with woodchips and a sponge. According to Brad Weigel, they are most effective when pinned on a branch near woolly adelgid. Brad Weigel photo
Treatment
To revive hemlock stands, BRLT and CRCT service members clipped clusters of lady beetles onto the lower canopy branches using clothespins.
“When they arrive, they are ready to feed,” Weigel said. “Placing the beetles close to the adelgid is best. The goal is to have both species harmonize so the beetles can eat enough adelgid to keep the tree healthy without eating them all and diminishing their food source.”
In New England, the lady beetle’s sole food source is the woolly adelgid, making integration safe for biological control.
“Both species come from Japan,” Weigel said. “Their life cycles sync up; in a forest ecosystem, they keep each other in check. The goal is to mimic that balance here. Each female lady beetle lays around 300 eggs in her lifetime. This pilot will succeed if multiple generations survive.”
Pesticides and chemical treatments are a surefire way to eliminate invasive species, but both land trusts emphasized that releasing toxins into the ecosystem is counterintuitive.
“This nature-based option allows the critters to do the work for us,” Selman said. “We are leveraging the predator/prey relationship to let these species address the issue. More often than not, nature has the solutions to our climate challenges.”
Ecosystem services
When asked why mitigation matters, Weigel said the ecosystem is an interconnected web — when one species gets sick, it affects the whole.
The hemlock canopy creates a damp ecosystem home to a mixture of plants and animals, chiefly lichens, mosses, ferns, barred owls, salamanders, frogs, certain warblers and vireos, and winter wrens. Hemlock stands typically grow near streams. They keep the water temperature right for trout that require cold water. Without them, the aquatic ecosystem is transformed.
Until now, the best treatments for homeowners have been dormant oil or insecticidal soap. If you notice sick hemlocks on your property, start a conversation with your local land trust — it’s likely you can be part of the next lady beetle order.
The Brunswick-Topsham Land Trust also purchases lady beetles from Tree Savers.
“We’ve already seen a lot of public interest,” Selman said. “And we’re hopeful — if we all do our bit, we can make a real difference.”
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