Spotted Lanternfly Damage: What It Does to Your Trees

If you live in the Lehigh Valley, you've seen them. Spotted lanternflies have become an unavoidable part of Pennsylvania life since they were first discovered in Berks County in 2014. But what are they actually doing to your trees? Here's what you need to know.

What Spotted Lanternflies Do to Trees

Spotted lanternflies are sap-suckers. They use piercing mouthparts to tap into plant tissue and feed on the sugary fluids inside. While one lanternfly doesn't do much damage, hundreds or thousands feeding on the same tree create real problems.

The damage process:

• Sap loss: Heavy feeding drains the tree's energy reserves
• Wound creation: Feeding sites can become entry points for disease
• Honeydew excretion: Lanternflies excrete a sticky substance that coats everything below
• Sooty mold growth: Black fungus grows on the honeydew, blocking sunlight from leaves
• Stress accumulation: Weakened trees become vulnerable to other problems

Signs of Spotted Lanternfly Damage

On the Tree

• Oozing sap from feeding wounds (looks like wet streaks on bark)
• Wilting leaves despite adequate water
• Leaf curling, especially on new growth
• Branch dieback, starting at tips
• Overall thinning of the canopy over time

Around the Tree

• Sticky honeydew coating on leaves, cars, decks, and anything beneath
• Black sooty mold growing on surfaces (looks like soot or black powder)
• Wasps and bees attracted to the sweet honeydew
• Egg masses on trunks and nearby surfaces (fall through spring)

The Insects Themselves

• Adults (July-December): About 1 inch long with gray wings spotted with black dots; hind wings flash red when they jump
• Nymphs (May-July): Black with white spots (early stage) or red with white and black spots (late stage)
• Egg masses (September-May): Gray, mud-like coating covering rows of eggs on trees, rocks, outdoor furniture, vehicles

Which Trees Are Most Affected?

Spotted lanternflies feed on over 70 plant species, but they have preferences:

High Risk - Favorite Hosts

• Tree of Heaven (Ailanthus): Their preferred host—if you have one, you'll have lanternflies
• Black Walnut: Saplings and young trees can be killed
• River Birch: Extremely common ornamental that they love
• Red and Silver Maple: Heavy feeding common
• Willow: All species attract them

Moderate Risk

• Oak species
• Pine trees
• Cherry trees
• Apple and fruit trees
• Sycamore

Also Affected

• Grapevines (major agricultural concern)
• Hops
• Rose bushes
• Many ornamental plants

Will Spotted Lanternflies Kill My Trees?

Here's the honest answer: for most landscape trees, probably not directly.

To date, spotted lanternflies have been linked to the death of:

• Tree of Heaven (which most people consider a weed tree anyway)
• Grapevines (serious agricultural losses)
• Young black walnut saplings

Mature, established shade trees typically survive spotted lanternfly feeding. However, that doesn't mean there's no impact:

• Trees become stressed and weakened
• Stressed trees are more susceptible to other diseases and pests
• Growth may slow
• Trees may be less able to recover from other stresses (drought, storm damage)
• Multiple years of heavy feeding accumulate damage

What Can You Actually Do?

For Homeowners

Scrape egg masses (September-May):

• Check trees, outdoor furniture, cars, stone walls, firewood
• Scrape into a container of rubbing alcohol or hand sanitizer
• Don't just knock them to the ground—eggs can still hatch

Remove Tree of Heaven:

• This invasive tree is their favorite host
• Removing it makes your property less attractive to lanternflies
• Caution: improper removal leads to aggressive sprouting
• Consider herbicide treatment by a professional

Circle traps on trees:

• Sticky bands or funnel traps catch nymphs and adults
• Must be used carefully to avoid trapping birds and other wildlife
• Wrap with chicken wire if using sticky bands

Kill on sight:

• Stomp adults when you see them (they're slow)
• Every one you kill is one less laying eggs
• Not a solution, but reduces local population

Chemical Treatment Options

For valuable trees under heavy attack, insecticide treatment can help:

Contact sprays:

• Kill lanternflies on contact
• Must reapply regularly
• DIY options available at garden centers
• Won't prevent new lanternflies from arriving

Systemic treatments:

• Applied to soil or injected into trunk
• Tree absorbs insecticide into tissue
• Lanternflies die when they feed
• Longer-lasting protection
• Best applied by professionals for large trees

A Realistic Perspective

Here's what we know after a decade of spotted lanternflies in Pennsylvania:

• They're not going away. They've established permanent populations.
• Natural predators (birds, spiders, praying mantises) are starting to eat them, but not enough to control populations.
• Most mature landscape trees survive, even with heavy feeding.
• The honeydew and sooty mold are often more annoying than the tree damage.
• Young trees and certain species need more protection.

For most homeowners, a sensible approach is:

1. Scrape egg masses when you find them
2. Remove Tree of Heaven if you have it
3. Monitor your trees for signs of stress
4. Consider treatment for young trees or heavily infested valuable specimens
5. Keep trees healthy overall (proper watering, mulching) so they can tolerate stress
6. Accept that some level of lanternfly presence is now normal

When to Get Professional Help

Consider consulting an arborist if:

• A valuable or specimen tree is showing significant decline
• You want systemic treatment done properly
• You need help removing Tree of Heaven without it resprouting everywhere
• Multiple trees on your property are heavily infested
• Your tree was already stressed before lanternfly feeding

The Bottom Line

Spotted lanternflies are annoying, messy, and a legitimate threat to certain plants—especially grapevines and young trees. But for established landscape trees in the Lehigh Valley, they're usually a stressor rather than a killer.

Do what you can to reduce populations on your property, keep your trees healthy so they can tolerate the feeding, and save aggressive treatment for situations where it's truly needed. We're all learning to live with this pest, and most of our trees will too.