BREAKING NEWS — ORANGE COUNTY, California
Residents in several Orange County communities may have noticed mosquito-control trucks moving through their neighborhoods overnight.
The Orange County Mosquito and Vector Control District is carrying out another round of overnight treatments this week in parts of Buena Park, Cypress, La Palma, Los Alamitos, Rossmoor, Anaheim, Garden Grove and Stanton.
The treatments are scheduled for Sept. 2 through Sept. 4, mostly between midnight and 5 or 5:30 a.m.
The activity comes as Orange County remains under a HIGH West Nile virus risk rating and recent mosquito surveillance continues to detect the virus across the county.
Orange County Mosquito and Vector Control District:
Current Large Area Mosquito Control Efforts
Where Orange County Mosquito Treatments Are Happening
The current operation isn’t one single treatment covering all of Orange County. OCMVCD has divided the work into several areas and is using truck-mounted equipment overnight.
For Buena Park, Cypress and La Palma, treatments are scheduled Sept. 2, 3 and 4 from midnight to 5 a.m. using DeltaGard.
Los Alamitos and Rossmoor are scheduled for treatments on the same three nights from midnight to 5:30 a.m. using AquaDuet.
Another treatment area covers Anaheim, Garden Grove and Stanton, also scheduled for Sept. 2 through Sept. 4 from midnight to 5:30 a.m. using AquaDuet.
OCMVCD provides maps on its residential treatment page where residents can check whether a specific address falls within a treatment area.
OCMVCD:
Residential Truck-Mounted Treatments
Why Are Mosquito Trucks Out Again?
There’s an important distinction in the district’s treatment schedule.
OCMVCD lists the Buena Park, Cypress and La Palma operation as “Continuing treatment.” The Los Alamitos/Rossmoor and Anaheim/Garden Grove/Stanton operations are listed as being conducted because of “Mosquito abundance.”
That means it would be inaccurate to say that every treatment taking place this week was specifically triggered by a new West Nile virus detection.
At the same time, West Nile activity provides important context for what’s happening across Orange County.
The district says adult mosquito control can be used when mosquito numbers increase in a particular area or when virus activity is detected in mosquitoes. Decisions about larger mosquito-control applications are based on surveillance information and mosquito-borne disease activity.
West Nile Virus Activity Remains High in Orange County
The latest city-level surveillance data published by OCMVCD covers Aug. 24 through Aug. 28.
During that period, the district recorded 6,985 female mosquitoes and tested 345 mosquito samples, or pools. Eighty-two samples tested positive for West Nile virus.
Anaheim accounted for 20 positive samples during the reporting period. Garden Grove had 10, while Buena Park, Cypress and Los Alamitos each recorded one.
Across Orange County, the district’s table lists 682 West Nile-positive mosquito samples year-to-date.
OCMVCD:
Countywide Mosquito Abundance by City
OCMVCD currently lists Orange County’s overall West Nile virus risk rating as HIGH.
Orange County has also already reported human infection this season. The Orange County Health Care Agency announced on Aug. 5 that an Anaheim resident had tested positive, becoming the county’s first reported human West Nile virus infection of 2026.
At the time, County Health Officer Dr. Regina Chinsio-Kwong said multiple detections of West Nile-positive mosquitoes indicated that Orange County could be experiencing an intense West Nile season.
Orange County Health Care Agency:
First Human West Nile Virus Case of 2026
This Isn’t the First Round of Mosquito Treatments
The current operation is part of a much longer mosquito-control effort this summer.
OCMVCD records show Cypress received a DeltaGard treatment July 16 through July 18. Buena Park, Cypress and La Palma were treated Aug. 4 through Aug. 6, and Cypress and Los Alamitos were among areas treated Aug. 11 through Aug. 13.
Another round Aug. 26 through Aug. 28 included parts of Anaheim, Buena Park, Cypress, Garden Grove, Orange, Stanton, Westminster and Huntington Beach.
Now several of those communities are being treated again.
OCMVCD:
2026 Large Area Mosquito Treatment History
What Are the Trucks Actually Doing?
The district uses ultra-low-volume, or ULV, adult mosquito control for these operations.
Unlike treatments aimed at mosquito larvae developing in water, adulticiding is intended to reduce the number of adult mosquitoes already flying in an area.
OCMVCD says its adult mosquito control is conducted using ULV equipment and that public-health pesticides registered with the U.S. Environmental Protection Agency are used as part of efforts to reduce mosquito populations and mosquito-borne disease risk.
The treatments are conducted overnight, when most residents are indoors and conditions are more suitable for the application.
More Treatments Are Already Scheduled
This week’s operation isn’t necessarily the end of the mosquito-control work.
OCMVCD’s residential treatment schedule already lists another round for Anaheim, Buena Park and Fullerton on Sept. 9, 10 and 11.
The district also notes that treatments may continue during mosquito season if mosquito numbers remain elevated or mosquito-borne disease activity persists.
For residents, the basic prevention advice hasn’t changed. OCMVCD recommends eliminating standing water around homes, keeping window and door screens in good condition, and using mosquito repellent when needed.
Small containers can produce mosquitoes, so flowerpot saucers, buckets, toys, pet bowls and other places where water collects are worth checking regularly.
For more ways to reduce mosquitoes around your property, see PestMarket’s Mosquito Control Guide: