EARLYDETECTION
Finding SLF before it establishes in a new county or region is the highest-leverage action a citizen can take. This guide tells you exactly what to look for, when to look, and how to report it.
Each new county confirmation triggers quarantine and resources. Early reports from citizens have been the primary mechanism for detecting new county infestations — long before official surveys catch up.
Why Early Detection Matters
The difference between catching SLF in a new county in year one versus year three is the difference between containment and establishment.
Quarantine Triggers
A confirmed SLF sighting in a previously unconfirmed county triggers a state quarantine order for that county. Quarantine means regulated movement of materials that could harbor SLF — firewood, outdoor equipment, vehicles — which slows further spread dramatically.
Resources Follow Confirmation
State departments of agriculture allocate treatment resources, survey crews, and outreach budgets to confirmed counties. Without a citizen report triggering confirmation, new infestations can grow undetected and under-resourced for 1–3 growing seasons.
Research Data Value
Early detection reports help researchers map the precise spread front and identify the pathways (roads, rail corridors, nursery trade) by which SLF moves. This data directly informs where states focus interception efforts.
What to Look For by Season
SLF has a predictable life stage calendar. Knowing what life stage to look for in each month dramatically improves your detection probability.
Spring
April – June
Spring
April – JuneNymph emergence (1st–2nd instar)
Tiny black nymphs with white spots, roughly the size of a sesame seed in early April, growing to pea-sized by June. Found on smooth-barked hosts: Tree of Heaven, grape vine, hops, willow. Look at the base of stems and on the underside of leaves.
Where to look first: Tree of Heaven stems and nearby grape vines. Check canes close to the ground first — nymphs climb upward through the day.
Summer
July – August
Summer
July – AugustLate nymphs and early adults
Red and black nymphs (4th instar) through late July, then adults beginning in late July–August. Adults have gray forewings with black spots and brilliant red hindwings visible in flight. Found aggregating on Tree of Heaven, grape vine, and hops in large numbers.
Where to look first: Any TOH within 300 feet, especially in late afternoon when adults congregate on stems and trunks. Vineyards, hops yards, and ornamental grape plantings are high-priority in new areas.
Fall
September – November
Fall
September – NovemberAdults and egg mass deposition
Adults remain active through the first hard frost. Female SLF begin laying egg masses in September. Fresh egg masses look like a smear of light gray putty, roughly 1–2 inches long, covered in a waxy coating that darkens and cracks over winter.
Where to look first: Any smooth vertical surface: tree trunks, fence posts, stone walls, outdoor furniture, vehicles, and utility poles. Egg masses can be on virtually any surface — a systematic sweep of your property takes 15 minutes.
Winter
December – March
Winter
December – MarchEgg masses only (adults are dead)
Egg masses are the only life stage visible in winter. Aged masses lose the waxy coating and look like dried, cracked mud with visible rows of 30–50 seed-like eggs underneath. Winter is actually the easiest time to find them — deciduous trees are bare and masses on south-facing bark are highly visible.
Where to look first: Tree of Heaven trunks are highest yield in winter. Also check stone walls, wooden fences, and any south-facing surface. A single winter survey of your property can reveal what the previous season left behind.
Priority Trees to Check First
SLF will feed on over 70 plant species, but a small number of hosts carry disproportionately high populations. Survey these first.
Tree of Heaven
Ailanthus altissima
The definitive primary host. SLF populations on TOH are 10–50× higher than on other hosts. Always check TOH first.
All seasonsGrape Vine
Vitis spp.
Both wild and cultivated grape are heavily preferred by adults. Check stems and canes carefully during summer and fall.
July – OctoberHops
Humulus lupulus
Highly preferred host. Commercial hops yards in the SLF range have documented severe economic damage.
July – SeptemberBlack Walnut
Juglans nigra
A common native host. Adults feed on stems and branches. Check bark for honeydew accumulation and sooty mold as indirect evidence.
August – OctoberApple / Crabapple
Malus spp.
SLF feeds heavily on apple in orchard settings. Check trunks and scaffold branches in late summer. Egg masses on bark are common in fall.
August – NovemberWillow
Salix spp.
Smooth bark and preferred feeding tissue make willows — especially weeping willow — high-value survey targets in spring for early nymphs.
April – JuneThe Visual ID Challenge
Misidentification produces false reports that waste state inspection resources. Know the lookalikes before you report.
Spotted Grape Zygaenid Moth
Harrisina americana
Similarity
Black body with orange-red markings
How to Tell Apart
Much smaller (under 1 cm), moth body shape, wings held flat over back not tent-like. Common on grape vines in the same geographic range.
Issus coleoptratus
Issus coleoptratus
Similarity
Planthopper with similar posture to SLF nymphs
How to Tell Apart
Smaller, brown and mottled, lacking the distinct white-spotted black pattern of SLF nymphs. Present in Europe, not in the eastern US.
Other Planthoppers
Fulgoridae / Issidae families
Similarity
Similar resting posture, wing shape
How to Tell Apart
Most native planthoppers are smaller and lack the distinctive red hindwing of SLF adults. When in doubt, photograph and submit to iNaturalist for community ID before reporting to the state.
Box Elder Bug
Boisea trivittata
Similarity
Red-and-black insect found on trees in fall
How to Tell Apart
Flat true bug body vs. SLF's elevated planthopper posture. Red coloring is on the edges of the wings, not underneath. Very common and often triggers false SLF reports.
When in doubt, submit to iNaturalist first. The iNaturalist community of entomologists and SLF experts will ID your observation within hours in most cases. A community-confirmed ID is much stronger evidence for a state report than an uncertain self-ID.
Using iNaturalist for Reporting
iNaturalist is the most widely used citizen science platform for SLF documentation. A good submission provides real scientific value.
How to Photograph for ID
Dorsal (top-down) shot
The single most useful image. Shows forewing pattern, body shape, and position. Get as close as possible without disturbing the insect.
Lateral (side) shot
Shows the distinctive planthopper body profile and wing position. Helps confirm it's not a flat-bodied bug species.
Hindwing visible (in flight or disturbed)
Gently tap the surface near the insect to prompt a wing display. The red hindwing is diagnostic for SLF adults and impossible to misidentify.
Context shot
Photograph the insect on its host plant with enough of the plant visible to confirm the host. This adds data beyond the species ID itself.
Egg mass: intact and scraped
For egg masses, photograph the intact mass in situ, then photograph the individual eggs after scraping for scale. Both images together make for a clear, high-quality report.
Data That Matters
Beyond the photo, this information makes your iNaturalist submission more scientifically valuable:
Location accuracy
GPS to within 10 meters if possible. Turn off location rounding in your iNaturalist settings for new-county detections.
Life stage
Note whether it is an egg mass, nymph (instar if known), or adult in the observation notes.
Count
Approximate number — even a rough count ("~50 adults on one tree") is useful population density data.
Host plant
What species was the SLF on? If unsure, describe the bark and leaves and photograph the host.
Evidence of honeydew or sooty mold
Indicates established feeding, not just passing adults. Worth noting in the description.
iNaturalist is not a substitute for your state department of agriculture report in unconfirmed counties. Always submit to both — the state report triggers the official response, iNaturalist feeds the research database.
State Reporting Portals
Each state has its own reporting mechanism. Find yours and bookmark it before you need it.
What Happens After You Report
Understanding what the state does after receiving your report sets realistic expectations and helps you follow up effectively.
Report intake and triage (1–5 days)
Your report enters the state's tracking system. In high-volume periods (peak adult season in already-confirmed counties), intake may be slower. New county reports are typically escalated for faster review.
Field inspection (1–4 weeks in new counties)
For unconfirmed counties, a state inspector will typically conduct a site visit to verify the sighting. They may contact you for access to the location. Have your photos and GPS coordinates ready.
County confirmation or non-confirmation
If the inspection confirms SLF, the state will formally add the county to the confirmed list and issue any necessary quarantine updates. If the inspector cannot find SLF, your report remains in the system as an unconfirmed sighting.
Quarantine order update (new counties)
Formal quarantine updates typically follow confirmation within days to weeks. This triggers regulated material movement requirements for businesses operating in that county.
Building a Personal Survey Route
Systematic personal surveys of the same route over time are far more valuable than random observations. Here is how to set one up:
- 1
Map a 0.5–1 mile walking route near TOH, grape, or wooded edges
Prioritize routes that pass Tree of Heaven and any cultivated or wild grape. A consistent start and end point matters for repeatability.
- 2
Set calendar reminders for key survey windows
April 15 (nymph emergence check), July 15 (early adult check), September 1 (peak adult + egg mass), November 1 (winter egg mass baseline).
- 3
Log each survey in a simple spreadsheet
Date, duration, weather, SLF life stages observed, estimated counts, host plants. Ten minutes of logging per survey creates a multi-year dataset.
- 4
Submit each positive sighting to iNaturalist
Even in confirmed counties, consistent observations from the same location contribute population trend data to researchers.
Related Guides
SLF Lookalikes
Full visual guide to insects that look like SLF — with side-by-side comparison photos and field ID tips.
Read more →TOH Removal Guide
Removing Tree of Heaven eliminates the primary host — the single best long-term early-detection advantage.
Read more →Report to Your State
Find your state's official SLF reporting portal and submit a confirmed or suspected sighting.
Read more →Weekly Fight Briefing
Season alerts, new guides, and weekly action prompts — personalized to your zip code. Free.