Spotted Lanternflies in Pennsylvania: What Homeowners Need to Know Now (July–August)
They look harmless at first, but these colorful little invaders can quietly destroy your trees, wreck your garden, and turn your backyard into a sticky mess.
Last summer, our neighbor was in a panic because the grapevine that she had nurtured for over a decade was suddenly withering. The leaves curled. Sticky residue covered the patio. Her backyard looked like it had been rained on… but it hadn’t.
The cause? Spotted lanternflies.
These pests aren’t just an annoyance. The spotted lanternflies drain sap from plants, leaving behind a sugary substance called honeydew. That honeydew attracts mold, ants, and wasps, and damages outdoor furniture, garden tools, and even cars.
Right now, from late July through early August is when the spotted lanternflies are the most destructive and visible.
Lifecycle Breakdown: What’s Happening Now?
Late July into early August marks a pivotal stage in the lanternfly’s life cycle here in Pennsylvania. If you’re in the Keystone State, you’re likely seeing fourth-instar nymphs transitioning into emerging adults, and their impact ramps up significantly.
Lifecycle of spotted lanternflies
- Egg masses overwinter from September through spring and hatch between late April and early June.
- 1st to 3rd instar nymphs (black with white spots) are active from May to early July.
- 4th instar nymphs (now active) appear in late July—larger, red with black-and-white patterns, and known for their strong jumping.
- Adults begin to emerge in late July and early August. They’re about 1 inch long, gray with black spots, and display bright red wings when startled.
Why This Stage Matters:
This is the most destructive time of the lanternfly season, and it’s especially important for homeowners to pay attention.
Fourth-instar nymphs and newly emerged adults are aggressive feeders. They pierce the stems of plants and trees to suck sap, which stresses your trees and vines especially when infestations are heavy. This feeding doesn’t just weaken the plants; it can significantly reduce fruit yield and even kill young or vulnerable trees.
As they feed, lanternflies excrete a sticky substance known as honeydew, which rains down onto whatever is below—leaves, decks, patio furniture, cars, even children’s play equipment. This sugary coating invites black sooty mold to grow, which can interfere with photosynthesis and create slippery, unsightly surfaces. It also attracts other pests like ants and wasps, creating an even bigger nuisance around your yard.
What makes this stage even more concerning is the increased mobility of the adults. While they prefer jumping or walking, they are capable of short flights …. they can travel between properties and spread infestations to new areas. This is when you’ll start seeing them on fences, trees, and siding.
And although egg laying doesn’t typically begin until September, the adults you see now are actively mating and preparing for it. Soon, they’ll begin depositing clusters of gray-brown egg masses on nearly any vertical surface such as tree bark, rocks, sheds, patio furniture, and even vehicles. Not sure how to handle those gray egg masses on your lawn furniture or firewood pile? This helpful guide from Better Homes & Gardens walks you through safe and simple removal.
What You Should Do:
✅ Inspect Your Trees & Garden
Check trunks, grapevines, and fence posts for red-and-white nymphs and spotted adults. Tree of heaven is their favorite, but they also target maple, walnut, willow, and ornamental plants.
✅ Take Action Now
Squash nymphs and adults on sight. Use neem oil or insecticidal soap for heavy clusters. Sticky bands (with protective wire) can help trap nymphs. Adults, however, often escape traps, so handpicking remains effective.
✅ Remove Egg Masses Early
While most egg-laying begins in September, some early masses appear by late August. Scrape them into a bag with rubbing alcohol or hand sanitizer and dispose.
✅ Report Sightings
If you see clusters or new infestations, report them to Penn State Extension or the PA Department of Agriculture. Your report could help prevent further spread.
Spotted Lanternfly Timeline (Homeowner’s Guide)
| Timeframe | Stage | What to Look For | Action Step |
|---|---|---|---|
| April–June | Nymphs 1–3 | Small, black with white spots | Monitor plant stems and lower trunks |
| July–August | 4th instar → Emerging Adults | Red-and-white nymphs; spotted gray adults | Destroy nymphs/adults, inspect trees/furniture |
| August–Sept | Adults Mating | Fully winged adults, often grouped | Begin egg mass cleanup and continued control |
| Sept–Oct | Egg Laying | Grayish waxy egg clusters | Scrape eggs, treat surfaces, report activity |
Late July through early August is your best window to act. At GrowsMows, we’ve seen firsthand how quickly these pests can overrun a property. Catching them now before they spread further or lay eggs is key.
For a deeper look into safe, effective control methods that may work for homeowners in northern Pennsylvania too, explore the University of Maryland Extension’s lanternfly management guide
Help Keep Lock Haven Landscapes Lanternfly-Free
At GrowsMows, we care about keeping our community’s yards healthy and thriving. If you’ve spotted signs of lanternfly damage or want help maintaining your lawn, we’re here to help.
Call or text us at 272‑261‑0581 to schedule a lawn care visit or just ask us your lanternfly questions. Let’s protect our plants, one yard at a time.
Email: Cole@GrowsMows.com
Serving: Lock Haven, PA and nearby neighborhoods
