Know Your
Season
SLF runs on a predictable clock. Miss the window, miss the impact. Here's what to do every month.
June: Nymph Season
4th Instars Appearing
Red-and-black 4th instar nymphs are emerging. This is the most visually striking stage — and a critical treatment window before adults appear. Circle traps, sticky bands, and dinotefuran sprays are most effective NOW.
Month-by-Month Action Calendar
January
Dormant- All SLF are in the egg mass stage
- Scrape egg masses — they're exposed and easy to find (no leaves on trees)
- Check vehicles, patio furniture, outdoor equipment
- Treat Tree of Heaven stumps with herbicide (dormant season is effective)
Note: Egg masses are most visible Jan–March before buds break
February
Dormant- Continue egg mass scraping
- Check firewood, pallets, any items stored outdoors
- Plan Tree of Heaven removal for late winter (cut before sap runs)
- Best time for ToH basal bark treatment with triclopyr herbicide
Note: Peak egg scraping month: every mass you scrape now = 30–50 fewer nymphs in May
March
Watch- Eggs still viable — keep scraping
- Late March: check for early nymph hatch if temps are above 50°F consistently
- Final window for Tree of Heaven removal before sap runs hard
- Review and set up circle trap sites for May deployment
Note: Mid-March MD: statewide quarantine in effect — all counties
April
Hatching- First nymphs (1st instar) typically hatch late April in DC/MD/VA
- 1st–3rd instars: tiny black with white dots
- Set up circle traps on high-value trees now
- Apply imidacloprid soil drench to trees (takes 4–6 weeks to absorb)
- Continue scraping any remaining egg masses (unhatched)
Note: Scraping deadline: assume all masses will hatch by May 1
May
Nymph Season- 1st–3rd instar nymphs in full force
- Check circle traps and empty weekly
- Apply systemic insecticides (dinotefuran or imidacloprid) — trees absorbing nutrients in spring
- Spray nymph clusters with pyrethrin or neem oil on contact
- Report sightings via the sighting map — early data shapes researcher response
Note: Best treatment window for systemic insecticides
June
4th Instar Emerging- 4th instar (red-and-black) nymphs appearing by mid-June
- Circle traps at peak effectiveness
- Dinotefuran bark spray — fastest systemic option
- Identify and map Tree of Heaven near you — report at the sighting map
- Watch for early adult emergence by late June
Note: High urgency: adults will begin appearing by July
July
Adults Emerging- Early adults appear by early-mid July in DC/MD/VA
- Squish adults on sight — especially females before they feed to maturity
- Check grapevines, hops, and ornamentals daily
- Dinotefuran sprays still effective
- Squish Cam — document your kills
Note: Adult SLF begin secreting honeydew — look for shiny leaf surfaces and sooty mold below trees
August
Peak Adult Season- PEAK SEASON — adult populations at maximum
- SLF swarm on host plants, especially at dusk
- Stomp/squish adults aggressively — each female can lay 2 egg masses
- Circle traps catching hundreds/day in heavy areas
- Alert neighbors — community coordination matters now
Note: Highest kill potential of the year
September
Pre-Egg Season- Adults still active but beginning to seek egg-laying sites
- Maximum squishing priority before females lay eggs
- Check all surfaces for early egg masses (some females lay in Sept)
- Continue circle traps
Note: Every adult female killed now = 30–50 fewer next year
October
Egg Season Begins- Adults dying from first frosts
- Females actively laying egg masses Sept–Oct
- Scrape any egg masses found immediately
- Check vehicles before traveling — SLF hitchhike on car undercarriages
- Treat Tree of Heaven with basal bark herbicide before dormancy
Note: Carcasses appear — still reportable, confirm presence
November
Dormant Soon- Adults dying, egg masses now the only live SLF
- Begin systematic egg mass scraping campaign
- Best month to start because leaves have dropped — masses visible
- Treat ToH root sprouts with glyphosate before frost
- Clean outdoor furniture, pots, vehicles before storing
December
Egg Season- All SLF in egg stage
- Scrape egg masses — same as January/February
- Check firewood before bringing indoors
- Assess season: how many did you kill? Log in kill tracker
- Plan Tree of Heaven removal for late winter
Season at a Glance
Egg Scraping Season
November – April
Egg masses are the only live SLF. Scrape them now to eliminate next season.
Nymph Season
April – June
Circle traps and systemics most effective. Hatch in late April, 4th instars by June.
Adult Season
July – November
Peak squishing window. Adults swarm in August. Females lay eggs Sept–Oct.
Related Resources
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