Are Mosquitoes Bad in New Hampshire?
NH hosts approximately 48 mosquito species (UNH Extension) and tracks three arboviruses: EEE (~30% fatality), West Nile Virus, and Jamestown Canyon Virus. In typical years, NH is mid-burden — but in outbreak years it leads the nation for EEE (2024: 5 cases, 1 death; 2005: 7 cases, 2 deaths). The worst regions: Rockingham County for EEE (Kingston-Brentwood-Danville swamps), Merrimack Valley for WNV (Manchester/Nashua catch basins), and the Seacoast/Great Bay for raw nuisance biting. NH has the weakest formal mosquito-control infrastructure in New England — no statewide board, no districts, no aerial spraying.
At a Glance
- Short Answer: Mid-burden most years, but NH leads the nation in EEE outbreaks
- Key Fact: 48 species; 3 arboviruses tracked; 5 human EEE cases in 2024
- NH Relevance: Weakest mosquito-control infrastructure in New England — no statewide board, no districts, no aerial spraying
- Action Needed: Region-specific: Rockingham County residents need professional-grade protection Aug–Sep
Are Mosquitoes Bad in New Hampshire — The Numbers
48
Mosquito species in NH
#1
NH's national EEE rank in 2024
30%
EEE case fatality rate
0
Mosquito control districts in NH
The Full Picture
The honest answer is: it depends on where you are in New Hampshire and what year it is. NH is not Florida or Minnesota for sheer mosquito volume. But NH has a disease risk profile that punches far above its weight — the state has led the nation in EEE cases multiple times, and has the weakest formal mosquito-control infrastructure in New England. Here's the regional and species breakdown.
48 Species, 3 Arboviruses, and a Structural Problem
UNH Extension puts the species count at 48; NH DHHS conservatively says 'more than 40.' Most don't pose health risks.
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The three tracked arboviruses: Eastern Equine Encephalitis (first NH human case 2004, ~30% fatality), West Nile Virus (first NH human case 2003), and Jamestown Canyon Virus (19 locally acquired cases since 2013). The structural problem: NH has no statewide mosquito control board, no regional districts, and no aerial spraying program. Towns hire private contractors individually. Massachusetts, by contrast, operates 11 mosquito-control districts with aerial capability.
Regional Risk Breakdown
Rockingham County: Highest EEE risk in the state.
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The acidic hardwood swamps of the Kingston-Brentwood-Danville-Hampstead corridor are the premier Culiseta melanura habitat. All 5 human EEE cases in 2024 fell in southeastern towns. Merrimack Valley (Manchester/Nashua/Concord): NH's West Nile hotspot. Urban catch basins are Culex pipiens breeding grounds; Manchester has run its own arbovirus program since 2000. Seacoast/Great Bay: Enormous Ochlerotatus cantator biting pressure from salt marshes — high nuisance, historically less disease. Strafford and eastern Hillsborough counties: Elevated EEE risk. Lakes Region and North Country: Heavy nuisance populations from shoreline wetlands but labeled 'Baseline/No Data' by DHHS because trapping is limited to the southeast.
The 2024 Outbreak: NH at #1 Nationally
NH tied Massachusetts at 5 human EEE cases in 2024 and recorded the first U.S. EEE death of the year — Steven Perry, 41, of Hampstead (NBC Boston).
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All five cases clustered in southeastern towns: Hampstead, Kensington, Derry, Newmarket, and Danville, with symptom onset August 5–18. This wasn't a one-off: NH led the nation in 2005 (7 cases, 2 deaths) and had 3 cases / 2 deaths in 2014. EEE cycles on a roughly 5–10 year regional periodicity.
How NH Compares to Neighboring States
In 2024: Vermont had 2 human EEE cases (first since 2012) with 86 positive mosquito batches across 16 towns.
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Massachusetts had 5 EEE and 7 WNV human cases with 11 mosquito control districts providing aerial response. Rhode Island had 1 EEE and 6 WNV cases. Maine had 1 EEE and 2 WNV cases. Connecticut had 0 EEE but 9 WNV cases. NH and Massachusetts tied for most human EEE, but Massachusetts has vastly superior control infrastructure.
What Makes Bad Years Bad
Heavy summer rainfall (the 2023 floods preceded the 2024 outbreak) boosts Culiseta melanura and floodwater Aedes vexans.
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Paradoxically, drought increases WNV risk because Culex and birds concentrate at shrinking water sources (Cape Cod Mosquito Control 2025). Mild winters improve Culex diapause survival. And the climate angle: NH winters have warmed faster than first-frost dates, meaning overwintering Culex survive better. Aedes albopictus — a daytime biter already established in Vermont since 2019 — is expected to push into NH as winters warm.
Bottom line — NH mosquitoes are manageable most years but genuinely dangerous in outbreak years. The lack of state-level control infrastructure means homeowners — especially in Rockingham County and the Merrimack Valley — bear more responsibility for protection than their Massachusetts or Connecticut counterparts.
Why This Matters in New Hampshire
NH's mosquito problem is really two distinct problems. The nuisance problem is driven by Aedes vexans and other floodwater Aedes, peaks 7–14 days after every summer storm, and is a drainage problem homeowners can largely solve. The disease problem is driven by Culiseta melanura (EEE in acidic swamps) and Culex pipiens (WNV in urban catch basins), operates on multi-year ecological cycles tied to bird populations and rainfall, and cannot be solved at the parcel level. NH's weak control infrastructure — no districts, no aerial capability, trapping concentrated in the southeast — leaves the Lakes Region and North Country as surveillance blind spots.
Key Local Data
2024: 5 human EEE cases, 1 death (Hampstead), ~10 EEE-positive and 3 WNV-positive mosquito batches. 2005: 7 EEE cases, 2 deaths. 2014: 3 EEE cases, 2 deaths. Rockingham County is the state's highest-risk area. Manchester has operated its own arbovirus program since 2000. NH has ~38 private mosquito-control contractors but no public districts.
We serve these communities
Service Area Map
Southern New Hampshire
Seasonal Mosquito Activity in NH
Jan
Dormant — all species overwintering in various stages
Feb
Dormant — no outdoor biting activity
Mar
Dormant — Culiseta melanura larvae begin development when crypt water reaches 9°C
Apr
First Aedes hatch from snowmelt; nuisance begins in southern NH
May
Spring broods building; floodwater Aedes active after rain
Jun
DHHS arbovirus season opens; first trap positives (JCV detected Jun 6, 2023 in Keene)
Jul
Nuisance biting peaks statewide; disease risk becomes detectable
Aug
Peak disease transmission — all 2024 EEE cases onset Aug 5–18
Sep
Highest overall EEE/WNV risk; Concord first frost avg Sep 27
Oct
Declining — DHHS hotline closes Oct 31; scattered late-season activity
Nov
Rare bites in sheltered river valley microclimates first week
Dec
Dormant — zero outdoor biting
DIY vs. Professional Treatment
An honest comparison to help you choose the right approach for your situation.
DIY Methods
What you can do yourself
High for nuisance Aedes; limited against swamp-breeding EEE vectors
Walk property weekly May–Sep; dump all containers within 48 hrs of rain
High personal protection — 5+ hours per application
Essential Aug–Sep in Rockingham County and Merrimack Valley
High in treated water; 30-day protection
For rain barrels, low spots, ornamental ponds; approved under NH F2 license
High — physical barrier against all species
UNH Extension: single most effective intervention Aug–Sep
Professional Treatment
Licensed applicators
85-90%
Reduction
21 days
Per treatment
$75–150
Per visit
Professional barrier sprays provide 85–90% Aedes reduction for 21 days — filling the gap left by NH's absent public control infrastructure
Licensed technicians identify breeding sources homeowners typically miss: catch basins, French drains, sub-slab moisture, low spots
Seasonal programs match the full Jun–Oct DHHS arbovirus window with monthly treatments
Critical for Rockingham County properties near known Culiseta melanura swamp habitat
Professional monitoring and treatment of Culex pipiens breeding sites (catch basins, storm drains) in Merrimack Valley communities
No obligation · Same-day service available
Our Honest Recommendation
DIY source reduction handles the nuisance problem for most NH homeowners. But if you live in or near the Rockingham County EEE corridor or Merrimack Valley WNV zone, professional barrier treatments during August–September are a genuine safety measure — not a luxury. NH's lack of public mosquito control means your property is your responsibility.
How Long Does Each Method Last?
Longer bars = longer protection from a single application.
CDC-recommended; apply 1 hr before to 2 hrs after sunset Jul–Sep
Most effective single action; weekly tip-and-toss breaks the 7–14 day cycle
85–90% Aedes reduction; 6–8 treatments per NH season
Approved under NH's F2 pesticide license; safe for pets/birds
Monthly treatments with source reduction; essential near EEE hotspots
Prevention Checklist
Consistent prevention is the most effective long-term strategy. Follow these steps to break the breeding cycle on your property.
7
Action Items
15 min
Weekly check
Same-day service available · No obligation
Know your regional risk: Rockingham County for EEE, Merrimack Valley for WNV, Seacoast for nuisance volume
Weekly tip-and-toss walks May through September — dump every container within 48 hours of rain
Apply DEET 20–30% or picaridin 20% for all outdoor evening activities July through September
Wear long sleeves and use screened porches during the August–September EEE/WNV peak — UNH Extension calls this the single most effective intervention
Treat undrainable water with Bti larvicide dunks, approved under NH's F2 pesticide license
Monitor NH DHHS arboviral bulletins for positive mosquito batches in your area
Support your town's mosquito-control contracting — NH has no state-level program to fall back on
Live in southern NH? Your mosquito risk is higher than you think.
NH led the nation in EEE cases in 2024 — and has no state mosquito control program. Professional treatment fills the gap.
Our Approach
Property Inspection
We identify every breeding source — gutters, downspouts, catch basins, and hidden standing water most homeowners miss.
Barrier Spray Treatment
85-90% mosquito reduction for up to 21 days. EPA-registered products applied to resting areas around your home.
Source Reduction
We treat standing water with Bti larvicide and recommend permanent fixes for chronic breeding sites.
Ongoing Protection
6-8 treatments per NH season (May-October). Each visit includes re-inspection and treatment adjustment.
Why Anchor Pest Services
Free inspection · No obligation · Same-day available
Frequently Asked Questions
NH Has No State Mosquito Program. We Fill the Gap.
Our barrier spray treatments reduce mosquitoes by 85–90% for up to 21 days. Serving Manchester, Nashua, Concord, and all of southern NH.
Sources & References
This article is based on publicly available data from the CDC, EPA, NH DHHS, and peer-reviewed entomological research. All sources are independently verifiable.
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Editorial disclaimer: This content is provided for informational purposes only and does not constitute medical or pest control advice. Every property is unique — consult a licensed pest control professional for guidance specific to your situation. Anchor Pest Services is licensed in New Hampshire (#782664).
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