HARRISBURG — A non-native, invasive insect that kills Eastern hemlock trees has advanced westward across Pennsylvania to Clarion and Jefferson counties, where infestations have been confirmed in two state parks.

“The hemlock woolly adelgid, a pervasive insect threat that has killed thousands of hemlocks across the state, has been detected in both Cook Forest State Park, Clarion County, and Clear Creek State Park in neighboring Jefferson County,” said Richard Allen, Department of Conservation and Natural Resources Secretary, in a news release.

“This discovery is especially unsettling due to the signature hemlocks in both parks’ forests.”

Home to the most significant Eastern hemlock stand north of the Smoky Mountains, Cook Forest State Park is famous for its old-growth trees. Its Forest Cathedral of towering hemlock and white pine is a National Natural Landmark.

It is home to some of the Eastern United States’ tallest hemlocks, including the celebrated Seneca Hemlock, the area’s third-tallest at 147 feet and 4 feet in diameter.

For this reason and in the face of the insect’s steady, northwestward spread, DCNR entomologists, foresters and park officials had ramped up early-detection efforts at the two parks. Attempts to delineate wooly adelgid infestation and chart feasible methods to combat its spread are under way, Allen said in the release.

DCNR will be embarking on a two-pronged treatment effort that relies on selective application of insecticides and the release of predatory beetles.

DCNR is partnering with the USDA Forest Service, The Nature Conservancy and other organizations to develop an Eastern hemlock management plan for northwestern Pennsylvania. In addition, its Bureau of Forestry is drafting a hemlock conservation plan for Pennsylvania.

The woolly adelgid is a fluid-feeding insect, easily detected by telltale egg sacs resembling cotton swabs that cling to undersides of hemlock branches. Introduced into the United States from Asia, it first was discovered in southeastern Pennsylvania in 1969 and steadily has been spreading westward. It now is in 56 of Pennsylvania’s 67 counties.

To learn about the woolly adelgid, go to www.dcnr.state.pa.us, click on “Forestry,” then “Insects and Disease” at upper left.

The Pennsylvania Parks & Forestry Foundation is accepting contributions to combat the insect at Cook Forest and Clear Creek state parks. Donation checks, payable to Pennsylvania Parks & Forestry Foundation, or PPFF, can be sent to Cook Forest State Park, ATTN: HWA Fund, P.O. Box 120, Cooksburg, Pa., 16217.