Like native species that are encouraged, nurtured, and enjoyed, invasive species have favorite homes.
Flying squirrels live in Chapman State Park. One of their preferred species of tree is the hemlock.
Those trees also provide cover and shade for other plants and animals - from songbirds to brook trout.
And, they are the home and food source of the hemlock woolly adelgid.
With the invasive species recently confirmed in Cook Forest in Clarion County, officials at Chapman were anxious to check their hemlock population.
On Tuesday, Dale Luthringer, environmental education specialist at Cook Forest, joined Chapman Park Manager Jim McCorkle, Environmental Education Specialist Jen Moore, and Campground Host Bob Steele in an examination of dozens of Chapman hemlocks.
Their search turned up no sign of the adelgids that lead to high hemlock mortality wherever they are found.
"We didn't find hemlock woolly adelgid in the park," Moore said.
The officials looked at groups of trees in selected areas of the park.
"We checked at least 60 trees and that is a small sample when compared to the amount in the park," Moore said. "It doesn't take long to check over a hemlock."
"This is done by taking a branch and turning it over and looking for a white substance - which resembles small cotton balls - on the branch itself," she said. The adelgids do not attach to the tips of needles.
At Luthringer's direction, they examined a minimum of 10 branches on each tree, making sure to go all the way around the tree.
They looked at 10 trees in each area of the park in which hemlocks are present: along Penny Run, near the beach, at the amphitheater, and along the nature trail, the snowmobile trail near the lake, and the lowlands trail.
Although they found no trace of the invasive species, Chapman officials will remain vigilant.
"If hemlock woolly adelgid were to get a hold at the park, we would lose several hemlocks that provide cover and shade for other species of plant and wildlife," Moore said. "Brook trout depend on hemlock for shade. Losing the trout would impact fishing in the lake."
"The temperature of the streams would be impacted as well as the organisms that live in them," she said. "Extensive hemlock mortality leads to a loss of hemlock-dependent wildlife. Songbirds are especially at risk. We have northern and southern flying squirrels in the park and adjacent game lands. These animals depend on the hemlocks for survival. The northern flying squirrel is already an endangered species."
The adelgids can spread naturally about 15 miles in a year. They can be carried by the wind or by birds or other animals. A female lays up to 300 eggs several times a year.
The purple insects originated in Asia and feed on the sap at the base of needles. "Hemlock woolly adelgid feeding reduces new shoot growth, and causes grayish-green foliage, premature needle drop, thinned crowns, branch tip dieback and eventual tree death," Moore said.
Chapman officials will continue to look for adelgids and Luthringer has told them what to look for at certain times of year.
"Dale also told us that March and September are good times of the year to check the trees in these designated areas," Moore said. "The eggs hatch in March producing small reddish brown nymphs - also called crawlers - and disperse from the tree or settle near the base of the needles."
"We were also looking for very tiny black dots which are the crawlers," she said. "The crawlers are inactive in summer. Development resumes in September and partially grown hemlock woolly adelgid spend the winter on tree branches covered by the white woolly material they secrete."
"September is a good time to look for white on the underside of the branches," Moore said.
There are chemicals that can be applied directly to the tree or to the soil at the base of the trunk that will kill the insects without harming the trees themselves.
As a backup measure, officials have been planting trees of other species "in areas with lots of hemlock in case the trees begin to die off," Moore said.
"Everyone should get in the habit of checking a hemlock when they see one," she said. "Early detection is the key to preventing the spread of hemlock woolly adelgid."