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Fogging FAQs

Why is my area being fogged for mosquitoes? 

Mosquito control applications are made when Butte County Mosquito and Vector Control District (BCMVCD) monitoring activities have determined:

  • That mosquito populations have reached levels that threaten public health.
  • That incidences of mosquito-transmitted diseases have been reported in the area.
  • That the nuisance threshold for the general population has been exceeded.

Adult mosquito control (fogging) is implemented to reduce adult mosquito populations and lessen the risk of disease transmission to residents and their animals.

Local public health agencies, mosquito control districts, and news media work together to inform residents of the mosquito problem and current disease threat. These applications are done under the direct control of licensed professional applicators with specific training for this type of public health pest control.

What types of insecticides are used to control mosquitoes? 

In addition to eliminating breeding habitats, a variety of different products may be used to control mosquitoes, including biological and chemical products that control mosquito larvae or adults. Only products registered by the U.S. Environmental Protection Agency (EPA), and California EPA are used. All products are applied at ultra-low volumes, typically a few ounces or less per acre, by approved aircraft or ground sprayers. This low rate is highly effective and poses minimal exposure risks to people, animals, and the environment.

Two classes of insecticides, each combined with a synergist chemical, are commonly used for adult mosquito control:

  • Pyrethrins are the active ingredients in pyrethrum, an extract of the African flower Chrysanthemum cineriaefolium. Pyrethrins are natural insecticides that act by blocking chemical signals at nerve junctions.
  • Pyrethroids are the synthetic version of pyrethrins and act by blocking chemical signals at nerve junctions.

Mosquito fogging is done in areas where adult mosquitoes frequent; including residential and agricultural areas, marshes, and woodlands.

Most mosquito species are active in the early morning, evening, and nighttime hours when searching for a blood meal. It is also the time when winds are calm and the most effective adulticide applications can be made. Larvicidal mosquito control applications can be made at any time to standing water and other larvae habitats.

How will these insecticides affect me and my family? 

At the rates the District applies these products (3/4 oz or less per acre), they should not pose a significant risk to you or your family. These materials have been used extensively and successfully throughout the country for decades. However, it is always a good idea to remain indoors and keep windows and doors closed during applications. For more information on insecticides and health, consult the U.S. Environmental Protection Agency, which oversees the registration of these chemicals. The National Pesticide Information Center (NPIC) can also provide information through a toll-free number, 1-800-858-7378 or online.

For fogging schedule including locations see the District’s Fogging Notice page.

I have an air conditioner. Should I turn it off if fogging is scheduled in my area? 

If you have a window air conditioning unit, you can turn off the vent so that air is not brought in from the outside. Central air conditioning units cool recirculated air in your house. Since a central air conditioning unit does not pull in outside air, there is no need to turn it off.

Can pets go outside during fogging? 

The materials used for controlling mosquitoes used in accordance to the label are not harmful to animals. Many times, it is same materials used to treat cats and dogs for fleas and ticks. However, if you want to reduce your pet’s exposure, keep them inside during fogging.

Do the insecticides you use hurt bees and butterflies? 

The District’s application methods minimize impacts to insects like bees and butterflies because treatments are made during times of the day when they are not actively foraging and are protected by their hives or resting areas. Also, the dosages/droplet sizes are designed specifically for tiny insects like mosquitoes; much higher dosages would be required to cause significant harm to bees or butterflies which have many times the body mass of a mosquito. The District does not apply products to blooming crops or weeds. Finally, mosquito control districts have used EPA registered public health pesticides for decades with insignificant evidence of harm to these insects.

Will the adult mosquito treatment affect my swimming pool water, lawn furniture, play equipment, toys, etc.? 

Your swimming pool water and items found in your yard should not be affected. Applications are made in the very early morning hours or late evening hours and the materials we use break down rapidly in sunlight. While it is not necessary, if it makes you more comfortable, you may wash down your furniture and other items that may have been exposed to the spraying materials.

Will fogging hurt my vegetable or fruit garden? 

There is no evidence to suggest harm to fruits or vegetable gardens. Just as you normally would when buying produce from the store, wash your vegetables and fruit before you eat them.

How can I find out if fogging is taking place in my area? 

Residents are encouraged to sign up for fogging notifications to receive information on treatments occurring in their area.

When do fogging notifications go out? 

Fogging email notifications are generally sent out at least 24-hours in advance from when fogging will be taking place. During the weekdays, notifications may go out by 4:30 p.m. for work that will be conducted that same evening. Any fogging applications can be cancelled or rescheduled due to weather conditions or other unforeseen reasons.


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