Beetles released in Allegheny National Forest to combat invasive insect

Bradford, Pa. — The U.S. Forest Service announced the release of additional beneficial insects in the Allegheny National Forest to combat the non-native, invasive hemlock woolly adelgid.

Hemlock woolly adelgid is an invasive insect native to Japan and the Pacific Northwest. The adelgid poses a serious threat to eastern and Carolina hemlock, which are at risk of fatal infestations since they lack natural resistance.

Within its native range, hemlock woolly adelgid populations are kept under control by natural predators and hemlocks have adapted to the insect. However, in the eastern United States, natural predators of the adelgid are absent and native hemlocks are not adapted to the pest.

Biological control (biocontrol) is the use of a natural predator to manage pest populations. Four insect species are known to be effective biocontrols for hemlock woolly adelgid; predatory beetles (Laricobius nigrinus and L. osakensis) and silver flies (Leucotaraxis argenticollis and L. piniperda).

These species are native to the Pacific Northwest and Japan, where the adelgid is a common pest of local hemlocks.

MORE COVERAGE FROM OUTDOOR NEWS:

Ryan Rothstein: This deer hunter’s wish list for 2025? It includes eliminating cross-tagging of bucks in Minnesota

Christmas week chuckles: A mountain-naming controversy as Trump says he’ll rename Denali in Alaska

A large buck-doe harvest gap in Minnesota this year

Laricobius beetles are released as adults in the fall and feed exclusively on developing and adult hemlock woolly adelgid throughout the fall and winter while the adelgid is in the first of two annual generations.

Leucotaraxis flies are released as adults in the spring, with larvae preying on adelgid eggs throughout the adelgid’s laying season. When present on the same site in sufficient numbers, the two biocontrols work in tandem for increased predation across multiple adelgid  life cycle stages.

During October and November of 2024, more than 2,000 predatory beetles were released at several sites across the Bradford Ranger District of Allegheny National Forest.

In early October, roughly 1,000 L. nigrinus beetles were released at two sites near Yellow Hammer and Muzette.

In early November, roughly 1,000 L. osakensis beetles were released at two sites near Hector Falls. 

Previous hemlock woolly adelgid biocontrols were used in the Allegheny National Forest as part of the Integrated Pest Management and Hemlock Conservation strategy for the Allegheny Plateau.

Since 2020, approximately 5,600 predatory beetles and 7,300 predatory flies have been released at more than a dozen sites across the forest. All flies and beetles were provided by Cornell University and Virginia Tech, with technical support from U.S. Forest Service State, Private, and Tribal Forestry.