Common Tree Pests: How to Identify and Control Them
Tree pests destroy millions of trees across the United States every year. From tiny bark beetles that decimate entire forests to invasive borers that have wiped out species in whole regions, understanding these threats is essential for protecting your landscape. This guide covers the major pest categories, the top ten most destructive species, and practical strategies for prevention and control.
Quick Answer
The most damaging tree pests fall into four categories: borers (emerald ash borer, Asian longhorned beetle), bark beetles (southern pine beetle, mountain pine beetle), defoliators (spongy moth, tent caterpillars), and sap-feeding insects (aphids, scales, spotted lanternfly). Early identification is critical because boring insects can kill trees within one to three years if untreated. Look for D-shaped exit holes, sawdust at the base, canopy thinning, or unusual woodpecker activity. For any suspected borer infestation, contact a certified arborist immediately.
Major Tree Pest Categories
Borers
Wood-boring insects are the most destructive category of tree pests because they feed inside the trunk and branches where they are protected from predators and most pesticides. Borers attack the cambium layer and sapwood, disrupting the tree's ability to transport water and nutrients. Infested trees often show canopy dieback starting at the top, D-shaped or round exit holes in the bark, and sawdust-like frass accumulating at the base. The emerald ash borer and Asian longhorned beetle are the two most devastating borers currently active in North America.
Bark Beetles
Bark beetles are small cylindrical beetles that bore through bark to lay eggs in the inner bark layer. Their larvae create distinctive galleries as they feed, girdling and killing branches or entire trees. Bark beetles also introduce blue-stain fungi that block water transport. The southern pine beetle and mountain pine beetle have killed billions of trees across North American forests. Bark beetles typically attack stressed trees first, but during outbreak conditions they overwhelm even healthy trees through mass attack. Signs include pitch tubes (masses of resin on the bark surface), boring dust in bark crevices, and rapidly fading foliage turning from green to yellow to red.
Defoliators
Defoliating insects eat leaves or needles, reducing the tree's ability to photosynthesize. While healthy trees can usually survive one or two years of defoliation, repeated defoliation weakens trees and makes them vulnerable to secondary attack by borers and diseases. Major defoliators include the spongy moth (formerly gypsy moth), which feeds on over 300 tree species, tent caterpillars that build silk webs in branch crotches, and the winter moth that attacks deciduous trees in early spring. Japanese beetles skeletonize leaves of linden, birch, and many ornamental trees during summer.
Sap-Feeding Insects
Sap-feeding insects use piercing-sucking mouthparts to extract phloem sap from leaves, twigs, and bark. They include aphids, scales, mealybugs, and the invasive spotted lanternfly. While individual insects cause minimal damage, large populations weaken trees and produce copious honeydew that promotes sooty mold growth. The hemlock woolly adelgid, a sap-feeding insect from Asia, has devastated eastern hemlock populations from Georgia to Maine.
Top 10 Most Destructive Tree Pests in the US
1. Emerald Ash Borer (Agrilus planipennis)
Has killed hundreds of millions of ash trees since its discovery in Michigan in 2002. Larvae feed beneath bark creating serpentine galleries. Identified by D-shaped exit holes. Now present in 36 states. Learn more in our emerald ash borer guide.
2. Asian Longhorned Beetle (Anoplophora glabripennis)
Attacks maples, birch, elm, willow, and other hardwoods. Creates round exit holes the diameter of a pencil. Quarantine and eradication efforts have required removing tens of thousands of trees in affected areas. See our Asian longhorned beetle page.
3. Spongy Moth (Lymantria dispar)
Caterpillars defoliate oaks, birch, aspen, and over 300 other species. Outbreak years can strip entire forests. Two or more consecutive years of heavy defoliation often kills trees, especially when combined with drought stress.
4. Southern Pine Beetle (Dendroctonus frontalis)
The most destructive pest of pine forests in the southeastern US. Attacks loblolly, shortleaf, Virginia, and pitch pines. Mass attacks can kill thousands of acres of pine forest during outbreak years.
5. Mountain Pine Beetle (Dendroctonus ponderosae)
Has killed billions of lodgepole, ponderosa, and whitebark pines across western forests. Climate change has expanded its range northward and to higher elevations, enabling unprecedented outbreaks.
6. Hemlock Woolly Adelgid (Adelges tsugae)
Tiny sap-feeding insect identified by white, cottony egg masses at the base of needles. Has killed hemlock trees from Georgia to New England. Systemic insecticide treatments can protect individual trees.
7. Spotted Lanternfly (Lycorma delicatula)
Invasive planthopper from Asia that feeds on over 70 plant species including maples, oaks, and fruit trees. Produces heavy honeydew that promotes sooty mold. Spreading rapidly from its 2014 introduction in Pennsylvania.
8. Japanese Beetle (Popillia japonica)
Adults skeletonize leaves of linden, birch, crabapple, and roses during summer. Larvae (grubs) damage turf roots. While rarely fatal alone, repeated defoliation weakens trees and invites secondary pests.
9. Bronze Birch Borer (Agrilus anxius)
Native borer that attacks stressed birch trees, especially European white birch. Causes dieback starting at the crown and progressing downward. D-shaped exit holes similar to emerald ash borer. Prevention focuses on maintaining birch health through adequate watering.
10. Eastern Tent Caterpillar (Malacosoma americanum)
Builds conspicuous silk tents in branch crotches of cherry, apple, and crabapple trees in spring. Caterpillars emerge to defoliate surrounding branches. Healthy trees recover from a single defoliation event, but repeated attacks weaken them.
Recognizing Signs of Pest Damage
Early detection is the key to successful pest management. Learn to recognize these warning signs during regular walks around your property. For a more detailed guide to identifying insect damage, see our signs of insect damage in trees page.
Exit Holes in Bark
D-shaped (EAB), round (ALB), or tiny shot-holes (bark beetles)
Sawdust or Frass
Fine boring dust at the base or in bark crevices
Crown Dieback
Thinning or dying branches starting at the top of the canopy
Increased Woodpecker Activity
Woodpeckers feeding heavily on a trunk indicates insect larvae beneath bark
Leaf Damage
Skeletonized leaves, chewed edges, leaf mining trails
Sticky Honeydew
Shiny residue on leaves or surfaces below from sap-feeding insects
Use our tree diagnosis tool to help identify the specific pest affecting your tree, or run a tree health check for a comprehensive assessment.
Prevention Strategies: Integrated Pest Management
Integrated Pest Management (IPM) is the most effective and environmentally responsible approach to tree pest control. Rather than relying on a single treatment, IPM combines cultural practices, biological controls, and targeted chemical applications to keep pest populations below damaging levels.
- Plant the right tree in the right place. Native and well-adapted species resist pests better than stressed, poorly-sited trees. Avoid planting monocultures that create easy targets for species-specific pests.
- Maintain tree health. Deep watering during drought, proper mulching, and avoiding soil compaction keep trees vigorous enough to resist and recover from pest attacks.
- Monitor regularly. Walk your property monthly during the growing season and look for the signs described above. Catching infestations early dramatically improves treatment success.
- Encourage natural enemies. Birds, parasitic wasps, predatory beetles, and other beneficial organisms consume enormous quantities of pest insects. Avoid broad-spectrum pesticides that kill these allies.
- Use targeted treatments when needed. When pest populations exceed acceptable levels, use the most specific treatment available, whether that is hand removal, horticultural oil, Bt (Bacillus thuringiensis), or a targeted systemic insecticide.
When to Treat Yourself vs. Call a Professional
DIY Treatment Is Usually Adequate
- Aphid colonies on small to medium trees (strong water spray or insecticidal soap)
- Tent caterpillar webs you can reach (remove by hand or with a stick)
- Japanese beetles on small ornamentals (hand-pick into soapy water)
- Minor scale infestations on accessible branches (horticultural oil spray)
Call a Certified Arborist
- Any suspected borer infestation (emerald ash borer, Asian longhorned beetle, bronze birch borer)
- Bark beetle activity on pines or spruces
- Hemlock woolly adelgid requiring systemic trunk injection
- Large trees requiring high-pressure spray equipment
- Trees near water features where pesticide runoff is a concern
- Any pest you cannot confidently identify
Professional treatment costs vary widely. A preventive emerald ash borer treatment runs $100 to $250 per tree annually, while large-scale defoliator spraying may cost $500 or more. Compare this to the cost of tree removal, which ranges from $500 to $5,000 depending on size, and prevention is almost always the better investment.Find a certified arborist near you.
Related Guides
Frequently Asked Questions
What are the most common tree pests in the United States?
The most damaging tree pests in the US include the emerald ash borer, Asian longhorned beetle, spongy moth (formerly gypsy moth), southern pine beetle, mountain pine beetle, Japanese beetle, hemlock woolly adelgid, spotted lanternfly, bronze birch borer, and tent caterpillars. Each targets specific tree species and causes different types of damage, from boring into wood to defoliating canopies.
How do I know if my tree has a pest infestation?
Common signs of pest infestation include unexplained canopy thinning, premature leaf drop, holes in bark or leaves, sawdust-like frass at the base of the tree, woodpecker activity on the trunk, sticky honeydew residue on leaves or surfaces beneath the tree, webbing or silk masses in branches, and bark that falls away to reveal tunneling galleries underneath.
Can I treat tree pests myself or do I need a professional?
Minor infestations of surface-feeding pests like aphids, tent caterpillars, or Japanese beetles can often be managed with DIY methods such as hand removal, horticultural oil, or insecticidal soap. However, boring insects like emerald ash borer, Asian longhorned beetle, or bark beetles require professional treatment with systemic insecticides injected into the trunk or soil. Any infestation affecting a large or structurally important tree should be assessed by a certified arborist.
What is Integrated Pest Management (IPM) for trees?
Integrated Pest Management is a science-based approach that combines multiple strategies to manage pests with minimal environmental impact. For trees, IPM involves regular monitoring and correct pest identification, maintaining tree health through proper watering and mulching, encouraging natural predators like parasitic wasps and birds, using targeted treatments only when pest populations exceed damage thresholds, and choosing resistant tree species when planting new trees.
When is the best time to treat trees for pests?
Timing depends on the pest. Preventive treatments for borers like emerald ash borer are best applied in mid-spring before adult beetles emerge. Defoliators like spongy moth are most vulnerable as young caterpillars in late spring. Systemic soil injections for sucking insects like hemlock woolly adelgid work best in fall. Contact your local extension office or a certified arborist to determine the optimal treatment window for your specific pest and region.
Protect Your Trees
Early detection and professional treatment can save trees worth thousands of dollars in property value. Preventive borer treatments cost $100 to $250 per tree annually, far less than the $500 to $5,000 cost of removal. Find qualified pest management professionals in your area through our arborist directory.