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Wide Area Residential Larval Control Spraying FAQs

What is Wide Area Residential Larval Control Spraying? 

Larval surveillance and control, which targets immature mosquitoes that may be developing in stagnant water in back yard sources is a critical component of any effective Integrated Vector Management (IVM) program. When mosquitoes are eliminated prior to becoming adults, they cannot pose a health threat or become a nuisance. Larval mosquito surveillance and control are the largest and most extensive aspects of the Butte County Mosquito and Vector Control District’s mosquito control program.

Why is the District carrying out wide area residential larval control treatments in my area and what will be achieved by carrying out this operation? 

Larval control is an important aspect of an effective mosquito control program. It helps reduce mosquito populations in areas with high mosquito counts to protect the health of residents from mosquito transmitted diseases such as West Nile virus. The District wants to reduce the number of immature mosquitoes developing in variety of back yard sources. If mosquitoes are targeted while they are still in the water, they will not have the opportunity to become flying adults that can bite and become a public health threat. Mosquitoes found in this area are more than a nuisance and can transmit West Nile virus. This disease is widespread throughout Butte County and Hamilton City and these mosquito control treatments aim at reducing mosquito populations.

What pesticide is used? 

VectoBac® WDG which is environmentally friendly, approved for application on organic crops, and registered with the U.S. Environmental Protection Agency and the California Department of Pesticide Regulation. The active ingredient in this product is Bacillus thuringiensis israelensis (BTI), a microbe found naturally in soil. For more information, please visit the Product Manufacturer.

How does the product work? 

BTI is used to prevent mosquitoes at the larval stage from surviving in standing water. It makes proteins that are toxic to immature mosquitoes (larvae), preventing them from developing into flying adult mosquitoes. This may lessen the need to spray for adult mosquitoes in the future.

How safe is this product for me, my family, and my pets? 

Risk to the general public from the use of BTI is minimal. It has no effect on people, pets, plants, or wildlife at the amounts used for mosquito control. In fact, little to no direct toxicity to non-target insects has been observed with this product.

What can I expect to see or hear when a mosquito control treatment is in progress and how long will it last? 

You will see and hear a slow moving District vehicle down your street. The truck has a mounted fogger in the back that will be spraying out the material in small droplet sizes that resemble a very fine mist. The treatment will occur quickly and should last no longer than 45 minutes.

How can we limit our exposure to the product? 

The treatments will be conducted in the early morning or late evening hours. Residents may choose to stay indoors during and for 30 minutes following the application as a best practice to reduce exposure.

Is this product going to leave spots on my patio furniture or my car? 

After going back outside, residents should not see any visual signs of the treatment on their property. Repeated applications in other parts of the United States have shown no problems with spotting or staining on outdoor structures.

How long will BTI last in the environment? 

Since BTI is a biological agent, it tends to break down quickly in the environment, typically a few hours after sunlight.

Is there anything the community can do to help control mosquitoes? 

Mosquito control is a community problem. The District is urging residents to do their part to eliminate stagnant water around the home. Working together will increase our chances of ridding the mosquito from our community. Removing mosquito breeding sources is the best long-term solution to reduce mosquitoes on your property and the risk of disease transmission in your neighborhood.

  • Dump and drain standing water around your property.
  • At least once a week check your back yard and drain any stagnant water from buckets, pet dishes, plant saucers, tires, bird baths, wheelbarrows, and other containers.
  • Check gutters and drains for water.
  • Call the District at (530) 533-6038 or (530) 342-7350 to report mosquito activity.


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