- Author: Mackenzie Faith Patton
The invasive pest spotlight focuses on emerging or potential invasive pests in California. In this issue we are covering West Nile virus.
West Nile Virus Facts
West Nile virus disease was first reported in California in 2003 and has become the most common and serious vector-borne disease in California. With the exceptionally wet weather in 2023, reported cases of this mosquito-borne virus doubled compared to the previous year.
West Nile virus is spread by mosquitoes in the genus Culex. Usually, the virus passes between mosquitoes and birds, but mosquitoes can also transmit the virus to humans, horses, and other domestic animals.
Because mosquitoes can get the virus from birds, monitoring bird populations and recording dead birds is one of the most important ways to track this disease.
What can you do?
The best way to prevent the spread of West Nile virus is to reduce mosquito populations through controlling the mosquito larval stages. Whenever possible, standing water should be drained, since mosquito larva can grow in as little as a few ounces of water. Clean gutters and storm drains to ensure water does not collect there. In areas that cannot be drained or mosquito-proofed, such as ponds, neglected pools, or unsealed rain barrels, there are some biocontrol options like Bacillus thuringiensis (Bt) that can reduce mosquito populations. In addition to these preventative measures, protect yourself from adult mosquito bites by using mosquito repellents or wearing long-sleeved shirts and long pants.
For more information on mosquito control and protecting yourself from mosquito-borne diseases, visit the UC IPM pages on mosquitoes. To report dead birds and view more information on West Nile in California, visit Westnile.ca.gov.
[Originally featured in the Spring 2024 edition of the Home & Garden Pest Newsletter]
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- Author: Anne Schellman
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.
Invasive Mosquitoes
West Nile Virus
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
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
Resources
California Department of Public Health https://www.cdph.ca.gov/Programs/CID/DCDC/pages/Aedes-aegypti-and-Aedes-albopictus-mosquitoes.aspx
EPA https://www.epa.gov/mosquitocontrol/general-information-about-mosquitoes
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.
/h3>/h3>/h3>/h3>/h3>As summer quickly approaches and we find ourselves getting outside a bit more, remember to take care to protect yourself from mosquitoes.
According to Gary Goodman, District Manager of Sacramento Yolo Mosquito and Vector control, many residents are anxious and excited to get outside and enjoy the warm weather so it's important to protect yourself from mosquito bites by wearing a good mosquito repellent.
The Centers for Disease Control and Prevention (CDC) recommend using an insect repellent that contains the active ingredients DEET, Picaridin, IR3535 or the plant-based oil of lemon eucalyptus. Aside from personal protection against mosquito bites, it's important to ensure mosquitoes are not breeding at home. Drain stagnant water from sprinklers, irrigation, and rainstorms. Be sure to check your backyard and dump any water in flower pots, kiddie pools, tires, pet dishes, bird baths and other common household containers that can hold water.
Another ongoing concern is the invasive mosquito Aedes aegypti which has been detected in several counties throughout Southern California and the Central Valley. For county level information, see this map. Invasive mosquitoes pose a significant health threat because they can transmit dangerous viruses including Zika, dengue fever and chikungunya. Surveillance efforts have continued since the initial detection last August. To date, no cases of Zika virus have been reported in California.
For more information on mosquito identification and management, see our recently revised Pest Notes: Mosquitoes. Additional information on vector-borne diseases is available on the California Department of Public Health website.
(Credit: James Gathany, Centers for Disease Control and Prevention)
In the newly revised Pest Notes: Mosquitoes, you'll find general mosquito prevention tips as well as information on the most recent mosquitoes to become established in California: species in the Aedes genus which can transmit Zika virus and other deadly diseases.
This publication, written by UC Riverside entomologist William Walton and UC Davis entomologist Bruce Eldridge, discusses the life cycles and virus transmission cycles of Culex and Aedes mosquitoes.
You will find tips on managing water barrels and other water capture structures to keep mosquitoes from breeding in them. There are updates on chemical control, including new personal use repellent products and outdoor sprays, and a link to a frequently updated map of Aedes mosquito detections from the California Department of Public Health.
Read the full Pest Notes: Mosquitoes on the UC IPM website for more information and continue to stay safe and healthy out there!
/div>- Author: Karey Windbiel-Rojas
- Author: Elaine Lander
Whether you're having a backyard barbecue or enjoying outdoor activities as the weather warms up, it's important to protect yourself from mosquitoes and their bites. Not only can these buzzing insects be a nuisance, certain mosquito species can transmit West Nile virus and other public health threats in California.
Late spring rains followed by warm, sunny days can create the perfect mosquito breeding habitat. Mosquitoes need very little standing water to lay eggs that can hatch in as little as one day. So remember, drain after the rain to fight biting mosquitoes!
What should you do to protect yourself? If possible, avoid being outside at dawn or dusk when mosquitoes are most active. When outdoors, protect yourself and your family by dressing in long sleeves and pants, or wearing an effective mosquito repellent. The best repellents are those that contain DEET, Picaridin, or Oil of Lemon Eucalyptus.
You can also help reduce mosquito populations by:
- Dumping standing water out of buckets, tires, flowerpots, and any other containers in your yard.
- Cleaning clogged rain gutters and storm drains.
- Keeping screen doors and windows in good condition so mosquitoes can't enter the home.
- Reporting neglected swimming pools or ponds in your neighborhood to your local Mosquito and Vector Control agency. They will come inspect, and in most cases, they can release mosquito-eating fish in these pools instead of spraying pesticides.
For more information, see the UC IPM Mosquitoes web page or read our Quick Tips on Mosquitoes.
Mosquito repellents are considered pesticides. Always read and carefully follow all precautions and safety instructions provided on the container label. Following the repellent or other pesticide label directions will ensure you are using it as intended and getting the best protection possible.