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Cytospora canker, also known as perennial canker, peach canker, Valsa canker, and Leucostoma canker, can cause trees in young orchards to die. Infected trees in older orchards slowly decline.

Armillaria root rot, sometimes called shoestring root rot, is caused by various species of the fungus Armillaria.

The elongate hemlock scale, sometimes known as the fiorinia scale, is a serious armored scale insect pest on ornamental and forest hemlock trees in Pennsylvania.

The euonymus scale is a key pest of euonymus, pachysandra, and bittersweet. This armored scale insect is native to Japan and China.

The European pine sawfly is common in Pennsylvania. The larval stage feeds on the needles of pine trees in landscapes, nurseries, and Christmas tree plantations.

The fall webworm is a widely distributed native pest that appears from late summer through early fall. It feeds on many species of deciduous trees and shrubs.

The European pine shoot moth is a key pest of ornamental pine plantings, pines in production nurseries, and Christmas trees in Pennsylvania.

The black vine weevil is a serious pest in nurseries and established landscape plantings.

The boxelder bug frequently becomes a nuisance pest around homes and buildings near plantings of the boxelder, Acer negundo.

The boxwood leafminer is a serious pest of Pennsylvania plantings of boxwood, Buxus spp.

The boxwood psyllid is a common pest of boxwood, Buxus spp. It is not considered as destructive as other boxwood pests.

There are a variety of gall-forming species of small wasps that commonly infest oak trees in Pennsylvania.

The magnolia scale is one of the largest scale insects in the United States. It feeds only on magnolia.

The Japanese maple scale is a recently detected pest of a wide range of woody host plants in Pennsylvania.

The pine needle scale is a key native pest of pine, Douglas-fir, spruce, and cedar in landscapes, nurseries, and Christmas tree plantations in Pennsylvania.

The potato leafhopper has been noted on more than 200 host plants, many of which are ornamental plants. However, this insect is best known as a field crop pest.

The rhododendron borer is a native pest of rhododendron, sometimes attacking mountain laurel and deciduous azaleas growing adjacent to infested host plants.

The snailcase bagworm is a moth (family Psychidae) that was accidentally introduced into the United States from Europe in the 1940s.

The cottony maple scale is one of the largest and most conspicuous soft scale insects that attack ornamental deciduous plants.

The eastern spruce gall adelgid is a key pest of Norway spruce, Picea abies, in northeastern United States.

The honeylocust plant bug is a key pest of honeylocust. It is a particular concern with the thornless cultivars grown in nurseries and used in landscapes.

In much of Pennsylvania, the hemlock woolly adelgid has caused significant damage to eastern hemlock in ornamental plantings and the forest.

The birch leafminer is a key pest of gray birch and paper birch trees.

The oystershell scale is a common armored scale insect that causes injury to shade trees and shrubs, most often lilac, ash, dogwood, maple, poplar, and willow.

The white pine weevil is considered the most destructive insect pest of eastern white pine in North America.