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County to Conduct First Mosquito-fighting Larvicide Drop of 2025

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Date: Apr 17 , 2025
Category: News & Announcements

San Diego County’s Vector Control Program is scheduled to conduct its first routine aerial larvicide drops of the year next week on Wednesday, April 23rd and Thursday, April 24th.

A total of 52 local waterways, including San Elijo Lagoon and San Dieguito Lagoon, will be treated to help curb mosquito populations and reduce the risk of diseases like West Nile virus. Every year from April through October, the County conducts these drops using special helicopters to apply solid, granular larvicide to hard-to-reach areas such as rivers, streams, and ponds.

This larvicide is completely safe humans or pets but is highly effectively in eliminating mosquito larvae before they mature into biting adults.

This is just one of the many ways the County helps protect public health during mosquito season. Most areas by hand or by truck (about 1600 sites countywide), but use a helicopter for hard-to-reach areas of standing water that can't be treated from the ground.

Aerial treatment schedule - 2025

  • April 23 (and 24 if needed)
  • May 14 and 15
  • June 4 and 5
  • June 25 and 26
  • July 16 and 17
  • August 6 and 7
  • August 27 and 28
  • Sept 17 and 18
  • October 8 and 9 (if needed)

Treatment dates are subject to change depending on conditions.

Please note, aerial larvicide application dates are subject to change depending on conditions.

If you would like to sign up to receive e-mail notifications of scheduled aerial applications, you can subscribe here. 

If you encounter a mosquito problem in your neighborhood, reach out to the County Vector Control Program:

Protect Yourself & Your Home

Residents should also help protect themselves from mosquitoes in and around their homes by finding and dumping out standing water to keep the pests from breeding. Getting rid of mosquito-breeding sites is critical to lowering the number of mosquitoes in our community. A mosquito only needs a tiny bottle cap-size pool of water to lay up to 300 eggs, which is why removing standing water is critical.

The Basics: 

  • Do not leave standing water in watering cans, empty after each use.
  • Do not let ANY water sit in drip pans under plants. Place sand or fine gravel in the drip pans. Make sure pots are draining well and there are no puddles, even tiny ones can become a breeding ground.
  • Fix any leaky faucets and hoses. Mosquitoes can breed in the water that pools underneath them.
  • Water can collect in cans, bottles, toys, coffee cups, pet bowls, etc. Clear your patio of any potential breeding debris. 
  • Mosquito fish may be picked up free of charge at different locations throughout San Diego County.

Protect yourself from mosquito-borne illnesses by wearing long sleeves and pants or use insect repellent when outdoors. Use insect repellent that contains DEET, picaridin, oil of lemon eucalyptus, or IR3535. Make sure screens on windows and doors are in good condition and secured to keep insects out.

Some useful mosquito (and other vectors) information can be found on the County of San Diego’s vector control website and useful fact sheets on preventing mosquito breeding and protecting against mosquito bites can be found here.