VISALIA, CA – World Mosquito Day marks the day in 1897 that Sir Ronald Ross discovered that female mosquitoes transmit malaria to people. This historic discovery laid the foundation for scientists to understand the deadly role of mosquitoes not only in malaria but also yellow fever, filariasis, dengue, West Nile virus (WNV), Zika and many other mosquito-borne diseases across the world. With this understanding came the development of tools and techniques to fight back.

Fed up with the numerous malaria cases and severe mosquito problem, the Visalia Woman’s Civic Club led Visalia residents to form the Delta Mosquito Abatement District in 1922. While malaria no longer poses a major threat to Tulare County residents, the fight against mosquitoes still continues. Other mosquito-borne diseases, such as WNV, threaten district residents every summer. Additionally, Aedes aegypti, an invasive mosquito species, brings the risk of new diseases, such as Dengue, Chikungunya, and Zika virus, making mosquito control just as important today as it was in the early 1900s.


A female mosquito taking a blood meal

Although malaria is no longer a threat to Central Valley residents, mosquitoes like this Culex quinquefasciatus female can still spread harmful diseases.


Delta Mosquito and Vector Control District encourages people to help control mosquitoes in their yards by dumping standing water at least once a week. Standing water is any source of water that does not evaporate in 3 days. Mosquitofish, available for free from the District, can be placed in larger water sources such as ponds and animal water troughs. Mosquitofish can eat up to 3 times their body weight in mosquito larvae a day.



Mosquitofish can eat up to 3 times their body weight in mosquito larvae everyday. They are available for free from Delta Mosquito and Vector Control District.


Residents can also prevent mosquito bites by using an Environmental Protection Agency (EPA)-registered insect repellent whenever they go outside. EPA-registered insect repellents have a registration number on their labels and include one of the following active ingredients:

  • DEET
  • Picaridin
  • IR3535
  • 2-Undecanone
  • Oil of Lemon Eucalyptus (OLE)
  • Para-methane-diol (PMD)

Always read and follow instructions on the product label to ensure maximum effectiveness.

August 20, 2021 – World Mosquito Day Press Release