California Mosquito Control: Larvicides Dominate, Naled Up 63 Percent
Key result: California’s public health pesticide use, mostly mosquito control, totalled 636,665 pounds in 2023. Larvicide types listed by EPA were 77.5 percent of applications and 75.2 percent of pounds. Naled, an adult mosquito spray most often applied from aircraft, rose from 65,507 pounds in 2022 to 106,621 in 2023.
The public side of pest control
Most of what this site covers is pest control businesses working on buildings. Mosquito control is different: it is done mainly by public agencies, and our guide to mosquito control districts explains who they are. What they actually apply is recorded in California’s pesticide use reports under site code 50, Public Health, which the department lists among the non-agricultural uses legally required to be reported, alongside vector control.
We extracted every public health record for 2022 and 2023, the two most recent years published: 9,575 and 9,341 records, covering 43 counties.
Larvae, not adults
| Type | Applications, 2023 | Share | Pounds, 2023 | Share |
|---|---|---|---|---|
| EPA-listed larvicides (Bti, Bacillus sphaericus, methoprene, mineral oil, surface films) | 1,278,543 | 77.5% | 478,454 | 75.2% |
| Spinosad and pyriproxyfen | 254,193 | 15.4% | 3,367 | 0.5% |
| Adult mosquito sprays and synergists (naled, malathion, pyrethrins, pyrethroids, piperonyl butoxide) | 61,755 | 3.7% | 142,388 | 22.4% |
| Other, including herbicides for vegetation | 55,878 | 3.4% | 12,455 | 2.0% |
Source: California Department of Pesticide Regulation, Pesticide Use Report 2023, site code 50, Public Health. Applications are summed per active ingredient, so a product with two active ingredients counts twice. Larvicide types from EPA’s guidance on controlling mosquitoes at the larval stage. Author calculation.
What it means. Public mosquito control in California is overwhelmingly a larval programme. EPA describes larvicides as targeting “larvae in the breeding habitat before they can mature into adult mosquitoes and disperse”. Bacterial larvicides, Bti and Bacillus sphaericus, account for the largest numbers of applications, and mineral oil, which smothers larvae at the water surface, for the largest weight: 368,539 pounds in 2023, 57.9 percent of the total. Sprays against adult mosquitoes are a small share of applications but a fifth of the pounds.
What limits it. Site code 50 covers public health use generally; it is mostly mosquito and vector control but not exclusively. The “other” group includes herbicides such as glyphosate used to clear vegetation from channels.
The naled increase
| Active ingredient | Pounds, 2022 | Pounds, 2023 | Change |
|---|---|---|---|
| Mineral oil | 319,003 | 368,539 | +15.5% |
| Naled | 65,507 | 106,621 | +62.8% |
| Bti (main strain) | 54,005 | 85,944 | +59.1% |
| Piperonyl butoxide | 13,940 | 19,494 | +39.8% |
| Bacillus sphaericus | 5,783 | 12,793 | +121.2% |
| Malathion | 4,775 | 6,257 | +31.0% |
| All public health use | 498,149 | 636,665 | +27.8% |
Source: Pesticide Use Reports 2022 and 2023, site code 50. Author calculation.
What it means. Public health pesticide use rose 27.8 percent by weight in a year. Naled, which EPA says is “most commonly applied aerially as an ultra-low volume (ULV) spray” and “used primarily for controlling adult mosquitoes”, rose 62.8 percent, in only 156 applications in 2023. Larvicides rose too. The reports do not record why; mosquito abundance, rainfall and disease activity all vary between years.
What limits it. Two years is not a trend. A small number of aerial applications can move naled’s total substantially.
Where it happens
What it means. Public health pesticide use is concentrated in the San Joaquin Valley: Kern, Tulare, San Joaquin, Madera, Merced and Fresno counties accounted for 56 percent of 2023 pounds. Orange County is the only coastal county in the top seven. This is the reverse of the map for structural pest control, which is concentrated in the coastal cities, as our county analysis shows.
Through the season
Public health use records peak in July and August, at 1,186 and 1,172 records in 2023, against 314 in January. The shape matches the mosquito season and mirrors, more steeply, the summer peak in structural pest control described in our monthly workload analysis.
Checks
1. Classification
Method. Larvicides are the types EPA lists: Bti, Bacillus sphaericus, methoprene, temephos, mineral oils and monomolecular films. Spinosad and pyriproxyfen are shown separately. Adult mosquito sprays are naled, malathion, pyrethrins and pyrethroids, with piperonyl butoxide, a synergist used in those products.
2. Replication
Result. EPA-listed larvicides were 79.1 percent of applications in 2022 and 77.5 percent in 2023; adult sprays 2.6 and 3.7 percent of applications, and 18.3 and 22.4 percent of pounds.
Download the data
The tables in this report are published as CSV files under a Creative Commons Attribution 4.0 licence. You may republish, remix and build on them, including commercially, with attribution to The Pest Control Brief and a link to this page.
- Public health pesticide applications and pounds by active ingredient and category, 2022 and 2023 (CSV, 200 rows)
- Public health pesticide pounds by county, 2022 and 2023 (CSV, 86 rows)
How to cite this report
The Pest Control Brief, “What California Sprays Against Mosquitoes: Larvicides Dominate, and Aerial Naled Rose 63 Percent in 2023”, 2 October 2026. https://thepestcontrolbrief.com/california-mosquito-control-pesticide-data/
References
- California Department of Pesticide Regulation. Pesticide Use Report annual archives for 2022 and 2023, site code 50. files.cdpr.ca.gov/pub/outgoing/pur_archives/. Accessed 4 October 2026.
- US Environmental Protection Agency. Controlling Mosquitoes at the Larval Stage. epa.gov larval stage. Accessed 4 October 2026.
- US Environmental Protection Agency. Naled for Mosquito Control. epa.gov naled. Accessed 4 October 2026.
- US Environmental Protection Agency. Bti for Mosquito Control (archived January 2017 snapshot). epa.gov snapshot, Bti. Accessed 4 October 2026.
- California Department of Pesticide Regulation. Pesticide Use Reporting. cdpr.ca.gov. Accessed 4 October 2026.
How the figures were built
Scope. Every 2022 and 2023 Pesticide Use Report record with site code 50, Public Health.
Measures. Pounds of active ingredient; applications from the application count field, summed per active ingredient; records.
Limitations. Site code 50 is not exclusively mosquito control. Two years. California only. Products sold to residents for their own use are not included.
Last reviewed: 4 October 2026.
For reporters
Most quotable statistics
- California’s public health pesticide use totalled 636,665 pounds in 2023, up 27.8 percent from 2022.
- EPA-listed larvicides were 77.5 percent of public health pesticide applications in 2023.
- Naled, an adult mosquito spray most often applied from aircraft, rose from 65,507 to 106,621 pounds.
- Six San Joaquin Valley counties accounted for 56 percent of public health pesticide pounds.
Press summary
Mosquito control in California is mostly a war on larvae, according to an analysis of state pesticide use reports by The Pest Control Brief. Larvicides listed by EPA, led by bacterial products and mineral oil, made up 77.5 percent of public health pesticide applications in 2023. Sprays against adult mosquitoes were under 4 percent of applications but over a fifth of the weight, and naled, most often sprayed from aircraft, rose 63 percent in a year. Most of the use is in the San Joaquin Valley.
Headlines editors could use
- California fights mosquitoes in the water, not the air
- Aerial naled use rose 63% in California in 2023
- The San Joaquin Valley’s mosquito chemistry
Questions
What do California mosquito districts spray?
Mostly larvicides: bacterial products such as Bti, mineral oil and methoprene. They made up 77.5 percent of public health pesticide applications in 2023. Adult mosquito sprays such as naled and pyrethrins were 3.7 percent.
Is aerial mosquito spraying increasing in California?
Naled, the main aerially applied adulticide, rose from 65,507 pounds in 2022 to 106,621 in 2023. Two years is not enough to call it a trend.
What is Bti?
Bacillus thuringiensis israelensis, a bacterium whose toxins, according to EPA, specifically target the larvae of mosquitoes, blackflies and fungus gnats.
Which California counties use the most mosquito control pesticide?
Kern, Tulare, San Joaquin, Madera, Merced and Fresno, together 56 percent of 2023 public health pounds.
Where can I get the data?
Both tables are in the CSV files above.
