Spotted Lanternfly (SLF)

Signs & symptoms

• Swarms of gray-and-red winged insects on trunks and branches, late summer into fall
• Sticky 'honeydew' coating leaves, trunks, decks, and anything under the tree
• Black sooty mold growing on the honeydew
• Wasps, bees, and ants gathering on the sugary residue
• Gray, mud-like egg masses on trunks and smooth surfaces in fall and winter

Spotted lanternfly took hold in our part of PA before almost anywhere else, and every year they show up in big numbers feeding on tree sap. They rarely kill a healthy mature tree outright, but they stress it — and a tree that's already weak, young, or fighting another problem can be pushed over the edge.

The bigger day-to-day headache for homeowners is the honeydew: the sticky mess they rain down coats patios, cars, and lower limbs, and then grows black mold. A heavily fed-on tree near your house is no fun to sit under.

What to do

• Scrape and destroy egg masses over the winter to cut down next year's numbers
• Keep an eye on young or already-stressed trees — those are the ones that can actually be harmed
• If a stressed tree near the house is declining or dropping limbs, we can assess it and clear what's a hazard

This is general guidance from three decades of tree work across the Philadelphia area — not a formal diagnosis. When it matters, we'll come look at the actual tree and give you a straight answer, free.

Trees we see this on

Frequently asked questions

Other tree problems