Spotted lanternfly (SLF, Lycorma delicatula) was first detected in NJ in 2018. Since then it has spread to all 21 counties. If you live in Piscataway, Edison, or anywhere in Middlesex/Somerset/Union you’ve almost certainly seen them — or seen the sticky “honeydew” mess they leave on cars, decks, and tree trunks.
Here’s what they actually do to your trees, what works to control them, and what doesn’t.
Quick identification by life stage
SLF has 4 visible nymph stages plus an adult stage, all visible May through November in NJ:
- Early nymphs (May–July): black with white spots, ~1/4″
- Late nymphs (July–Sept): red and black with white spots, up to 1/2″
- Adults (July–Dec): ~1″ long, gray forewings with black spots, bright red hindwings visible in flight
- Egg masses (Oct–May): putty-colored mud-like blobs about 1″ long on tree trunks, undersides of branches, lawn furniture, vehicles
What they actually do to trees
SLF feeds on tree sap by piercing bark with a needle-like proboscis. Two consequences:
- Sap drain stresses the tree. Heavy infestations (hundreds to thousands per tree) drain enough sap to stress mature hardwoods and kill saplings.
- Honeydew (excreted sap) coats everything below. The sticky substance attracts wasps, drips on cars and decks, and grows black sooty mold that turns leaves and bark dark.
The good news: SLF rarely kills mature trees outright, with one big exception. Tree of heaven (Ailanthus altissima) is SLF’s preferred host — and tree of heaven is itself an invasive species that’s usually worth removing on its own merits.
Trees most affected in NJ
- Tree of heaven (Ailanthus) — primary host, treat or remove
- Black walnut — high impact, especially on younger trees
- Silver maple, red maple — secondary hosts, sticky honeydew problem
- Willow, river birch — affected during heavy outbreak years
- Grapevines — hit very hard; commercial vineyards have been devastated
Oaks, hickories, and most fruit trees show light feeding but generally fare well.
What works for control
1. Egg mass scraping (October – April)
The single most effective DIY control. Each egg mass produces 30–50 nymphs. Scrape egg masses off trees, lawn furniture, vehicles, and any vertical surface using a credit card or putty knife. Drop scraped masses in alcohol or hand sanitizer to kill them.
Egg masses are easiest to find Nov–Mar when leaves are off trees and you can see the trunk clearly. We typically scrape 50–200 masses off mature trees on properties that haven’t been managed previously.
2. Sticky bands or circle traps (May – Sept)
Wrap tree trunks with sticky tape (or build “circle traps” that funnel nymphs upward into a collection bag). Catches climbing nymphs in early summer. Tradeoffs: sticky bands also catch beneficial insects, birds, and small mammals — circle traps are more selective.
3. Targeted insecticide treatment
For high-value trees (mature ornamentals, specimen trees, vineyards), systemic insecticide injection or basal bark spray with dinotefuran or imidacloprid provides season-long protection. Should be applied by a licensed pesticide applicator — not a DIY job.
4. Tree of heaven removal
If you have tree of heaven on your property, removing it eliminates SLF’s preferred host. But: don’t just cut tree of heaven. It re-sprouts aggressively from cut stumps and roots, often making the problem worse. Use a “hack & squirt” or basal bark herbicide treatment first to kill the root system, THEN remove. We can do this as part of regular service.
Soapy water sprays, vinegar, essential oils, ultrasonic devices, and most home remedies have no measurable effect on SLF populations. They’ll kill individual insects you spray directly but won’t protect the tree. Don’t waste money on lanternfly-marketed gadgets — the only proven controls are mechanical (scraping, banding) and chemical (proper insecticide application).
The state regulation angle
NJ has SLF quarantine zones covering most of the state. If you move firewood, mulch, or outdoor equipment between properties, technically you’re supposed to inspect first to avoid spreading egg masses. For homeowners this is mostly self-inspection — for commercial property managers and landscaping companies there are formal compliance requirements.
Got a heavy infestation?
For mature trees with serious SLF damage, or for properties with tree of heaven you want gone, we handle scraping, treatment, and removal. We can also work with commercial property managers on quarantine-compliance protocols.
The honest outlook
SLF is now permanent in NJ. The state isn’t going to eradicate it. What you can do is:
- Manage your own property aggressively (scraping, removing tree of heaven, treating high-value trees)
- Tolerate the visual nuisance on lower-value trees that won’t be killed by SLF
- Watch for the population dropping over the next 5–10 years as native predators (parasitic wasps, fungal pathogens) catch up — this is the typical pattern with invasive insects
SLF won’t kill your oaks. It will make your maple drip honeydew on your car. Treat the high-value trees, scrape what you can, and remove tree of heaven if you have it.
