Important Insect and Disease Pests
of Pennsylvania's Forests

Hundreds of insects have adapted to living and feeding on forest trees, and in most cases, without harm to the host. These species of insects have specialized their behaviors to reduce competition among themselves. For instance, one species may feed on roots and twigs, but not the leaves or the entire tree; whereas another will eat only leaves. By using these specific niche behaviors, the diversity of forest feeding/living insects has been able to flourish.

Most insects have a short life cycle and produce many offspring. Almost all of the offspring die before reaching adulthood. When more than the usual number of offspring survive to the adult stage, the numbers increase and develop into insect outbreaks. There are about a dozen species of insects which sometimes reach outbreak numbers and cause a lot of damage to forest trees. These can also be a nuisance for people who live, work or recreate in the forest.

Beech Bark / Beech Scale Complex
Eastern Tent Caterpillar
Fall Cankerworn
Forest Tent Caterpillars
Hemlock Woolly Adelgid
Leafrollers
Twolined Chestnut Borer
Scale Insects
White Pine Weevil
Spruce Gall Adelgids
Maple Anthracnose
Leaf Galls
Gypsy Moth
Fall Webworm
Black Knot Of Cherry
Elm Spanworm
Armillaria Root Disease

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