Fighting bugs with bugs, in Wiscasset

Chewonki site of predatory bugs’ release
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Tuesday, June 3, 2014 - 6:30pm
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adelgid, ladybird beetle
The cotton ball-like bugs are adelgid, which go after hemlocks’ starches; the larger, black bugs nearby are ladybird beetles that feed on the adelgid. This photo was taken on Chewonki Foundation land in 2013, at the release of 5,000 of the beetles. Courtesy of the Maine Forest Service

On Cushman Mountain, near the mouth of the Sheepscot River on Chewonki Foundation land in Wiscasset, it's bug versus bug.

The hemlock woolly adelgid is feeding on the starches in twigs of the beneficial hemlock tree. And hopefully, last year and again this year, another bug is feeding on it.

That bug, a ladybird beetle, relative of the well-known red and black ladybug, could be part of the answer to saving coastal Maine's hemlocks from the adelgid. The state's May 29 release of 1,500 of the beetles at Chewonki was the second release there in as many years. The 2013 deposit numbered 5,000, said Allison Kanoti, a forest entomologist with the Maine Forest Service.

About five or six Maine sites, including the one at Chewonki, have gotten or will get the predatory bugs this year, for the first time or a repeat deposit like Wiscasset's.

The location's selection followed an apparent uptick in its adelgid population. In 2011, less than one percent of hemlock branches there were noticeably infested; in 2013, more than 40 percent were, Kanoti said.

A single tree may have thousands on it, she said.

The adelgid looks like a tiny cotton ball. It has at least one edge over the all-black, ladybird beetle. It doesn't need to mate to reproduce, like the beetle does. And the adelgid reproduces in big numbers.

Kanoti doesn't know yet if the predatory bugs will help stem the adelgid population and save hemlocks in affected regions. “It’s too early to talk about success or failure,” she said. “Biocontrol is a long-term commitment.” Future options could include pinpointing a fungus that would target the adelgid, but spare other species.

Federal grants are funding this year’s beetle release.

Hemlock trees help shelter forest floors from erosion, and buffer water temperatures to the benefit of brook trout and other species, according to a Maine Department of Agriculture, Conservation and Forestry press release.

Kanoti encourages property owners to check out their hemlock trees with a hand lens to help spot adelgid. Sightings can be reported to the Maine Forest Service at 207-287-2431, or online at www.maine.gov/forestpests#hwa