Spotted Lanternfly inCook County, ILSPOTTED LANTERNFLY GUIDE
Cook County entered watch zone status in 2024 as spotted lanternfly populations in neighboring Indiana — including Lake County directly across the state line — raised the probability of imminent introduction into the Chicago metro. As the nation's second-largest rail hub, Chicago routes millions of freight car-miles annually through Cook County's southern industrial corridors, and the Calumet region's heavy freight traffic, intermodal yards, and truck routes along I-94 and I-80/94 (the Tri-State) represent some of the highest-risk SLF introduction vectors in the Midwest. Lake Michigan shipping adds a maritime dimension rarely seen in inland watch-zone counties. IDOA and Chicago-area agencies are prioritizing surveillance along the southern corridors nearest the active Indiana infestation front.
Highest activity zones
SLF Hotspots in Cook County, IL
Chicago South Side
Active zone
Calumet City
Active zone
Blue Island
Active zone
Harvey
Active zone
Midlothian
Active zone
Primary SLF food source
Tree of Heaven in Cook County, IL
Tree of Heaven is entrenched along virtually every railroad right-of-way in Cook County — from the freight mainlines threading through the Chicago South Side and Calumet industrial district to commuter rail margins throughout the suburbs. River margins of the Calumet River, Little Calumet River, and Chicago Sanitary and Ship Canal host dense Ailanthus stands. I-80 and I-294 underpasses in Harvey, Midlothian, and Blue Island are priority monitoring locations, as these structures accumulate wind-dispersed ToH seed and provide sheltered habitat where SLF egg masses may go undetected until populations are established.
Identify Tree of Heaven →Local action resources
What To Do in Cook County, IL
Report a Sighting
Every sighting in Cook County, IL maps the invasion front. Report directly to Illinois Dept of Agriculture (IDOA).
Report Now →Squish on Sight
See a spotted lanternfly? Kill it immediately — it is legal and encouraged in all states. Learn the best kill methods.
Full Fight Guide →Map ToH in Your Block
Tree of Heaven removal cuts off SLF food supply. Add ToH sightings to the community map to guide removal efforts.
View Sighting Map →Statewide resources
Full IL State Guide
County-level data, quarantine zones, treatment guides, and agency resources for the entire state.
See the full IL guide →Community intelligence
Live Sighting Map
See where SLF has been spotted near you in Cook County, IL. Add your own sighting to help map the front.
Open the Map →Free weekly fight briefing
Fight SLF in Cook County, IL.
One email per week. Your zip code. Your threat level. Your action plan. Know exactly what to do this week in Cook County, IL.