Common Tree Pests

Diseased Tree Bark

In the spring we expect to see leaves budding on our trees, but when they aren’t growing as expected it may be due to insect infestations and diseases they cause. Learn about insects common in southwest Pennsylvania and what can be done to prevent them.

Diseased Trees

As trees grow older or experience environmental stress, their ability to fight off infection from insects and disease is weakened and they are more likely to succumb to insect infestations. Common external stressors are drought, pollution, abnormal temperatures, excessive moisture, and wind damage. Taking time to properly care for your trees to promote their health is always a good practice that can aid your trees in fighting back against infection.

Tree Pest Control

It is important to understand the types of insects that can infect your trees and how to identify the damage. We’ve put together a shortlist of known pests in southwest Pennsylvania:

Emerald ash borer  

These insects are most harmful in their larval stage as they feed on ash trees under the bark that leads to tree death three to five years down the road. Signs of emerald ash borer infestation include bark splitting and flaking, D-shaped exit holes of adult beetles, and S-shaped larval feeding galleries just under the bark. Protecting against emerald ash borers requires a more systemic approach, such as soil injections, trunk injections, and lower trunk sprays of insecticide to prevent these borers from entering the tree, as should always be applied by certified professionals.

Gypsy moth 

Gypsy moth caterpillars primarily attack oak trees, but also a range of other trees and shrubs such as birches, willows, spruces, and pines, and result in heavy defoliation of the tree. Detecting potential gypsy moth infestations can be done in June and July by searching for tan egg masses on trees, stones, and other substrates. These eggs will hatch the following year in mid-April to early May. Removing dead branches, old wood, and building materials is one preventative step you can take. Approved insecticides are available to homeowners who are experiencing a gypsy moth infestation, but be sure to research this thoroughly to ensure you are complying with legal restrictions. 

Hemlock wooly adelgid  

Adelgids are small, soft-bodied insects that have piercing-sucking mouthparts that do damage to wooly trees. As hemlock trees are common in Southwest PA, the invasive of these non-native insects has resulted in considerable hemlock defoliation and mortality in state forests. Adelgids feed on sap which impairs tree nutrients and leads to needle drop, branch dieback, and in some cases tree mortality. Spotting cotton swab-like sacs on twigs is a sign of egg nests and potential problems so the regular examination of your trees is a preventative measure. While insecticides are available to treat this threat, harvesting and replanting is another option in addition to waiting to see if your hemlocks survive the infestation. 

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