- 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: Lauren Fordyce
Lately you may have seen some large, leggy insects bumbling around on your home, bouncing off walls and ceilings. What are these?
While many people call them “mosquito eaters” or “mosquito hawks,” they are actually crane flies. And unfortunately, they do not eat mosquitoes. Many reports claim that they bite or sting, and this is also false. The adults are harmless and many species don't even have mouthparts to feed at all! However, their larvae can be pests of lawns and turfgrass.
Larvae are to 1-1/2 inches long, brown, and wormlike with very tough skin. They may resemble white grubs, but crane fly larvae do not have legs. The majority of lawn damage from crane flies is seen along the Pacific Northwest coast. In California, damage has been found mostly in Humboldt and Del Norte counties, rarely in warmer, dryer inland areas of the state. Although, wet springs and waterlogged soils are usually associated with a higher populations of crane flies.
You can prevent crane flies in your lawn by properly irrigating and fertilizing. Adjust irrigation systems during rainy periods to avoid overwatering. Remove excess thatch and aerate you lawn to improve drainage. Reduce shady areas by pruning back tree branches to allow more light to reach the grass during the early morning and late afternoon.
Find out more about crane flies by reading the UC IPM Pest Notes: Lawn Insects.
Learn how to control mosquitoes around your home by visiting the UC IPM Pest Notes: Mosquitoes.
Mosquito Awareness Week, observed April 16 - 22, 2023, educates California residents about mosquitoes and how to help prevent the spread of mosquito-transmitted diseases.
One of the wettest years in history has left standing water across the state, creating perfect conditions for mosquitoes to develop. Stagnant water creates havens for disease-spreading mosquitoes, and mosquito experts are concerned this could be a long and intense mosquito season.
“After record amounts of rainfall this year, it is really important for all Californians to dump and drain standing water that has accumulated in their yards, porches, and patios,” said Assemblymember Jim Wood, who authored the state resolution recognizing California Mosquito Awareness Week. “It only takes a small amount of water for mosquitoes to develop so removing all stagnant water is a simple but very effective way to help to eliminate mosquitoes from our community. Not only are mosquitoes a nuisance, but they can transmit deadly diseases. Let's all work together to fight the bite!”
West Nile virus, spread by Culex mosquitoes, is the most prevalent and serious mosquito-borne disease in California. There is no human vaccine for West Nile virus, a disease which can cause debilitating cases of meningitis, encephalitis, and even death. In 2022, there were 209 human West Nile virus disease cases from 28 counties in California, including 13 human deaths.
In addition, invasive Aedes mosquitoes continue to spread throughout the state. First detected in 2013, they have spread to 25 counties and 300 cities and towns. These mosquitoes are very hard to control and pose a serious public health threat because they can spread diseases like Zika, dengue, chikungunya, and yellow fever to people and animal heartworm to pets.
According to the California Department of Public Health, since 2016 there have been nearly 900 California residents with travel-associated dengue infections. While there has not yet been local transmission of dengue in the state, it is occurring at California's borders, making the threat even more real. In 2022, the border state of Sonora, Mexico had more than 9,000 cases with 91 people dying from dengue. In December 2022 in Maricopa County, Arizona, two individuals tested positive for dengue, which they acquired locally from a mosquito bite.
“While all of the rain has been great for the drought, it provides mosquitoes with more places to lay their eggs,” said Wakoli Wekesa, PhD, president of the Mosquito and Vector Control Association of California. “As we work to keep Californians safe from mosquito-transmitted diseases and combat the spread of invasive Aedes, it's critical that residents take simple precautions to protect themselves and keep their communities mosquito-free.”
Mosquito experts say the future of mosquito control requires innovation to protect the public from mosquito-borne diseases. Mosquito and vector control agencies in California are exploring the potential use of three innovative technologies: self-limiting mosquitoes, Wolbachia, and irradiation. More information about the need for innovative technologies and how they work is available on the MVCAC website.
Everyone can do their part to help prevent mosquito bites:
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Apply insect repellent containing an EPA-registered active ingredient, including DEET, picaridin, oil of lemon eucalyptus, or IR3535, to clothes and exposed skin according to label instructions. Repellents keep mosquitoes from biting. It is important to follow EPA and CDC guidelines for the safe use of repellents on children.
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Dress in long sleeves and pants, especially if outside at dawn and dusk when mosquitoes that can spread West Nile virus are most active.
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Install screens on windows and doors and keep them in good repair to keep mosquitoes out of your home.
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Eliminate all sources of standing water on your property, including in flowerpots, old tires, buckets, pet dishes, and trash cans. Mosquitoes lay their eggs in very small amounts of standing water.
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Repair leaking faucets and broken sprinklers that can contribute to standing water around your home.
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Clean rain gutters clogged with leaves.
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Report neglected swimming pools and day-biting mosquitoes to your local mosquito and vector control agency (agency information can be found at www.mvcac.org)
To learn more, please visit the MVCAC website or the California Department of Public Health Mosquitoes and Mosquito-Borne Diseases webpage.
About MVCAC
The Mosquito and Vector Control Association of California (MVCAC) is the statewide voice for mosquito and vector control professionals. The association provides public health information, expertise, mosquito and vector-borne disease surveillance, innovative research, professional training, effective legislative and regulatory advocacy on behalf of California public agencies.
[Shared from the Mosquito and Vector Control Association of California. View UC IPM's Pest Notes: Mosquitoes for more information.]
- Author: Elaine Lander
- Editor: Karey Windbiel-Rojas
While many of you are preparing for the 4th of July holiday, we at UC IPM are also thinking about stars and stripes but in a slightly different way: yellow starthistle and striped skunks.
As you celebrate July 4th, be sure to cover up to avoid mosquito bites when outdoors and watch out for yellowjackets that may be foraging for food while you barbecue. If you're watching fireworks light up the sky, we hope you'll be reminded of dandelion puffballs “exploding” and sending their seeds in the wind to establish new plants (and then look up how to remove them).
If you are going camping, be sure not to move any invasive insects with you by buying firewood near your camping location. At the campsite, beware of raccoons, ants, and poison oak!
Wishing you a safe (and pest free) holiday!
From UC IPM Pests in the Urban Landscape blog.
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.
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