One early morning this past weekend while outside enjoying a cup of coffee, I noticed a cloud of mosquitoes buzzing around my legs. I jumped up and ran off. But too late! Not long after, I discovered at least 10 mosquito bites on my legs. I was annoyed but also a little concerned.
Aedes aegypti mosquito, CDC.
In years past, I would get bitten by mosquitoes when out late at night. But in the past decade, I've been bitten frequently during the day, and this year seems to be particularly bad, possibly due to favorable weather conditions for mosquitoes.
Why are mosquitoes biting during the day? It's because in 2011 and 2013, two invasive species of mosquitoes arrived in California. Unlike native mosquitoes that bite at dusk and dawn, Aedes egypti and Aedes albopictus mosquitoes bite during the day. Not only that, but they can also carry deadly viral pathogens such as Zika, dengue, chikungunya, and yellow fever viruses. The good news (so far) is that according to the California Department of Health, none of these viruses are known to be in California to date.
Culex quinquefasciatus feeding, CDC.
West Nile Virus
West Nile virus is carried by Culex mosquitoes, which were first found in California in 2003. Since then, 7,500 cases were reported, and 300 people have died. The disease is most serious in children, senior adults, and people with weakened immune systems. Virus symptoms range in severity. Some people experience no symptoms, while others can become very ill. In Stanislaus County this year, 4 people have been infected, but nobody has died.
Mosquito lifecycle US EPA
How can you protect yourself?
Although day biting mosquitoes can bite through clothing, it can help reduce bites. You can also wear an application of repellent underneath. The CDC recommends using an insect repellent containing the active ingredients DEET, Picardin, IR3535, or the plant-based oil of lemon eucalyptus. Please note, the last active ingredient is not an essential oil.
How to Prevent Mosquitoes
Female mosquitoes use your blood to help fertilize their eggs, which they lay in water. Incredibly, these eggs can hatch and live in something as tiny as a soda or water bottle cap. Prevent mosquitoes from hatching by emptying out containers around your landscape. If you like to provide water for birds and insects, make sure that it's circulating and does not get stagnant.
UC Master Gardener Walt Cooley inspects a bucket of water before dumping it out.
For more in-depth information and tips for how to protect yourself and your family in and around your home, visit the UC IPM Website at https://ipm.ucanr.edu/PMG/PESTNOTES/pn7451.html
California Department of Public Health https://www.cdph.ca.gov/Programs/CID/DCDC/pages/Aedes-aegypti-and-Aedes-albopictus-mosquitoes.aspx
UC IPM Pest Notes: Mosquitoes https://ipm.ucanr.edu/PMG/PESTNOTES/pn7451.html
West Nile CA https://westnile.ca.gov/
UC IPM Quick Tips: Mosquitoes https://ipm.ucanr.edu/legacy_assets/pdf/qt/qtmosquito.pdf or if you prefer in Spanish, https://ipm.ucanr.edu/legacy_assets/pdf/qtsp/qtspmosquitoes.pdf
Stanislaus County, Human West Nile Virus Cases in Stanislaus County, https://www.schsa.org/pdf/press-releases/2023/WNV%2023-06.pdf
Anne Schellman has been the UC Master Gardener Coordinator in Stanislaus County since the program started in 2018.