Hemlock trees in Schuylkill County have been suffering from hemlock woolly adelgid for years and there is no end in sight.
Laurie Goodrich, senior monitoring biologist at Hawk Mountain, said that blocks of trees all over the sanctuary have been damaged from the small aphid-like insect that originated in Asia.
"We lost some trees over the years," Goodrich said. "Some of them are hanging on and some of them are doing fine, so it's a mix."
Goodrich said that the damaged trees, which look half-dead this time of year, can be seen along the main trail or at the lookouts.
Susan Hyland, Master Gardener coordinator with the Penn State Cooperative Extension, said that while it has been called a pest since 1987, it was known to be in 33 counties in Pennsylvania in 1973.
She said that pretty much nothing can be done for hemlocks in forests since the insects spread from tree to tree so fast, but if private owners have a small number on their property, they can protect them.
According to Hyland, the insect is easily recognized most of the year by the presence of a dry woolly substance on young twigs, associated with all stages of the adelgid but is most abundant during spring when the egg masses are present. They look like cotton.
There are two generations of hemlock woolly adelgid per year.
Between March and April, adults of the overwintering generation lay 50 to 300 eggs each in a cottony mass.
The nymphs hatch in April and May, settling on the base of the needles where they insert their piercing and sucking mouthparts.
By mid-June, the generation matures and leaves the hemlock in search of another tree.
These insects then lay eggs that hatch in early July, settle on the cottony mass and remain dormant until the middle of October when feeding resumes.
Nymphs feed and develop during the winter and mature by spring.
Hyland said that since only some of these insects have wings, most leave the tree by attaching to other animals, such as birds, so she suggested that people with hemlocks on their property not hang bird feeders as it would only help spread the pests.
To get rid of the growths on trees, property owners can dislodge eggs and crawlers by directing a strong stream of water at infested branches periodically from April through June or clipping heavily infested twigs from branches, although extensive clipping may have undesirable effects on the appearance and health of the tree.
Infested trees should not be fertilized since fertilizing may increase the adelgid population.
One last treatment that Hyland said the extension suggests is using "soft pesticides."
Horticultural spray oil can be applied as a dormant treatment in early April.
Insecticidal soap or horticultural oil are 100 percent effective in controlling hemlock woolly adelgid since they are less toxic and help preserve populations of beneficial insects.
The spray needs to drench the branches completely, so this can't easily be done to large trees and can be expensive.
"You need to treat every year, for the life of you or the tree," Hyland said. "I've been treating three trees in my yard every year."
Information from Hyland also notes that sprays will not remove the white, cottony adult masses at the base of the needles and it is important to continue to monitor each year for egg-laying and crawler stages even if a chemical control is applied.
For more information, call the extension office at 570-622-4225 or email schuylkillext@psu.edu.