To better protect our communities and the environment, the Orange County Mosquito and Vector Control District applies mosquito larvicide by helicopter to mosquito breeding areas that cannot be treated by hand. These applications occur during the mosquito breeding season, as needed.

Mosquitoes are more than just a nuisance. They can transmit many serious diseases including West Nile virus and other viruses to people and animals. The symptoms of West Nile virus include fever, headache, chills, and rashes. In rare cases, the illness may progress to encephalitis, coma, and even death. For more information on West Nile virus, visit our West Nile Virus and West Nile Virus Threat pages.

The granular larvicide used by OCMVCD acts specifically on mosquito larvae and will not harm people, pets, plants, or wildlife. The larvicide consists of granules containing Bacillus thuringiensis israelensis (Bti) and Bacillus sphaericus. These naturally-occurring bacteria target mosquito larvae and prevent them from developing into biting adults. During larval mosquito control, a GPS-equipped helicopter applies the larvicide directly to areas of standing water where mosquitoes breed.