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Some mosquitoes carry West Nile Virus (WNV). Mosquitoes only need two tablespoons of water to breed, and water can collect just about anywhere. Each year, the City of Denton implements its Mosquito Surveillance and Response Plan. The main goal of mosquito control is to decrease the number of adult mosquitoes by eliminating breeding grounds wherever possible. Partner with the City to prevent WNV and protect yourself from mosquitoes.

Risk Levels

  • Risk Level 2 - Enhanced Response

    Condition: Probability of human outbreak is low

    Trigger: Normal mosquito activity with little or no evidence of arthropod-borne virus/disease. Enhanced response level is due to recent historical presence of arthropod-borne virus/disease in vectors, humans, or other hosts within the vicinity of Denton (approximately 100 miles).

    Risk Level 2 is enacted typically before the mosquito season is underway and information centers on activities citizens can do to help the City control the mosquito population. At this Risk Level, the probability of human outbreak of the West Nile virus is low. Strategies for protecting human health and methods for minimizing mosquito populations are the main control measures emphasized under Risk Level 2.

  • Risk Level 3 - Public Health Concern

    Condition: Probability of human outbreak is low to moderate

    Trigger: Arthropod-borne virus/disease isolated from mosquitoes collected during trapping activities at a single monitoring site.

  • Risk Level 4 - Public Health Warning

    Condition: Probability of human outbreak is moderate to high

    Trigger: Multiple mosquito pools collected at different times and locations test positive for arthropod-borne virus/ diseases. Single human case confirmed with laboratory testing

  • Risk Level 5 - Public Health Alert

    Condition: Human outbreak is confirmed

    Trigger: Multiple human cases.

The City is currently at Risk Level 5

Level 5 Response: Third Ultra-Low Volume Ground Spraying in Targeted Area

In accordance with the City of Denton Mosquito Surveillance and Response Plan, the City will conduct a second ground spray application of Merus 3.0, an organic, ultra-low volume (ULV) ground spray for killing adult mosquitoes, in designated residential areas north of McKinney Street, south of College Street, from Bolivar Street to Ruddell Street (see the map below). The spraying will take place between the evening/overnight hours of 9 p.m. on Monday, Sept. 21, and 5 a.m. on Tuesday, Sept. 22, when most residents are indoors and mosquitos are active. While not harmful to humans or pets, the late evening application allows residents to more easily avoid contact with these pesticides when they are applied.

Click here for a printable map of the spray area.

  • ULV Ground Spraying FAQs
    What pesticide product is used in ultra-low volume (ULV) ground sprayings?
    Merus 3.0 ™, an organic pesticide, will be used during ULVspraying of your neighborhood. The active ingredient is 5% natural pyrethrins, which is derived from flowers of chrysanthemum plants. Merus™ is a low-odor formulation with no petroleum distillates, is Organic Materials Review Institute (OMRI) listed. and meets National Organic Program (NOP) standards for adult mosquito control in and around organic gardens, farms and crops.

    How does ULV spraying work?
    ULV sprayers use large volumes of air at low pressures to transform pesticides in liquid form into droplets that are dispersed into the atmosphere.  ULV sprayers deliver very small amounts of pesticide optimized for mosquitoes. The dose is specifically designed for insects the size of mosquitoes.

    When will spraying be conducted?
    To minimize exposure, spraying will be conducted between 9 pm and 5 am, when most residents are indoors.

    How persistent is Merus 3.0 in the environment?
    Pyrethrins, the active ingredient in Merus™ 3.0, break down quickly in the environment and are non-persistent.  The half-life of pyrethrins in the presence of sunlight ranges from 4 to 8 hours.  Pyrethrins do not bioaccumulate.

    Will mosquito spray treatments harm humans or pets?
    Mosquito control treatments using EPA-registered products, when applied correctly, will not harm humans or pets.

    Could there be health concerns for pregnant women?
    As with all chemical exposures, pregnant women should take care to avoid them. 

    What kinds of precautions are recommended if spraying is scheduled in your area?
    The active ingredients of the pesticide product used for mosquito control generally break down quickly and do not leave a toxic residue. You can reduce/eliminate your exposure to the pesticide by staying indoors during spraying. Otherwise, no special precautions are suggested.
    Do you need to cover plants before a mosquito spray treatment? Are garden veggies safe to eat after a treatment?
    Plants and garden beds do not need to be covered or harvested before a treatment. Just use the same practice that should be followed with grocery or market produce and rinse with water and a mild detergent before consuming.

    What are the impacts of mosquito spray treatments on bees?
    Merus™ is toxic to bees when if the bees are exposed to direct treatment.  This would typically occur while bees are actively foraging, which occurs during the daytime. To minimize exposure, spraying will be conducted between 9 p.m. and 5 a.m. Impacts to bee colonies are not expected since bees are inside hives at night. Also, the dose used for spraying is specific to mosquitoes, which are much smaller than most beneficial insects, including bees. Registered beekeepers and local beekeeper associations are notified about the spraying in advance.

    Where can additional information about Merus™ 3.0 be found?
    Pesticide labels contain detailed information on how to use the product correctly and legally. Labels also contain information on potential hazards associated with the product and instructions that should be followed in the event of poisoning or spills. Merus™ information can be found at https://www.clarke.com/filebin/productpdf/merus3.0.pdf.

    A safety data sheet, or SDS, is written or printed material concerning a hazardous chemical that is prepared by the manufacturer or the company selling the product.  An SDS describes the physical and chemical properties of the product according to specific guidelines. The Merus™ 3.0 SDS can be found at https://www.clarke.com/filebin/productpdf/merus3.0-sds.pdf.

Click here for details about the first ground spray application on Sept. 8.
Click here for details about the second ground spray application on Sept. 11.
Click here for details about the third ground spray application on Sept. 21.

Tips & Resources

How to Get Rid of Mosquitoes: Eliminate Common Hangouts

Don’t give mosquitoes a place to stay by emptying standing water from these and other areas around your home and yard:

  • Open trash/recycling carts
  • Boats and pool covers
  • Fountains and bird baths
  • Clogged rain gutters
  • Low areas
  • Water bowls for pets
  • Buckets and barrels
  • Flower pots and saucers
  • Leaky hoses
  • Wagons and other toys
  • Ponds
  • Neglected pools
  • Tires
  • Piles of trash or debris

To treat stagnant water, use Bti briquettes, which is not a chemical. Each briquette will treat 100 square feet of surface water for 30 days. To apply, simply drop the briquette in standing water. Bti is available in limited supply from the City or can be purchased at local garden/hardware stores.

City Bti Distribution Locations

Residents will need to bring a valid driver's license and utility bill for proof of residence. The limit is two donuts per resident.

  • Customer Service, located at City Hall East, 601 E. Hickory St., Ste F. (Corner of Hickory Street and Railroad Avenue); Monday through Friday from 8 a.m. to 5 p.m.
  • City of Denton Composting, located at 1100 S. Mayhill Rd. in the Pecan Creek Water Reclamation Facility; Tuesday through Saturday from 7 a.m. to 3 p.m

Protect Yourself against Mosquitoes

  • DRAIN standing water around your home, yard, and neighborhood
  • DUSK and DAWN are the times of day you should try to stay indoors; this is when mosquitoes are most active
  • DRESS in long sleeves and pants when you’re outside, and spray thin clothing with repellent
  • DEFEND yourself by using an insect repellent that contains DEET, Picaridin, or Oil of Lemon Eucalyptus     

West Nile Virus and Symptoms

West Nile virus is a potentially serious virus that affects the nervous system. According to the Centers for Disease Control, it is established as a seasonal epidemic in North America, typically from late spring through summer and fall. This mosquito flies short distances (often much less than a mile) to feed. Adult mosquitoes have a life span of a few weeks during the summer months.

Symptoms usually appear within three to 15 days of being bitten. If you are concerned about any symptoms you or a family member are experiencing, see your health care provider.

About the Mosquito Surveillance and Response Plan

The program is a partnership between the City of Denton and the University of North Texas. This surveillance program collects adult mosquitoes that are sent to the Texas Department of State Health Services for testing. The overall goal is the use data on mosquito populations and mosquito virus infections rates to:

  • Assess the threat of human disease
  • Determine the geographical areas of highest risk
  • Determine the need for intervention events, and timing events
  • Identify larval habitats that are in need of targeted control
  • Monitor the effectiveness of control measures
  • Better understand transmission cycles and potential vector species

The use of ultra-low volume aerosols (”fogging”) will only be considered if there are conditions indicative of Risk Level Five (Public Health Alert) and if other control measures appear to be ineffective. If adulticiding is implemented, citizens residing in areas where applications will occur will be notified through several methods including Robocall, CodeRED, eNews, through this website, and on the City Facebook page.

Preventing Other Mosquito-Transmitted Diseases
If you are planning to travel to another country, visit the resources below to find out if the country has any travel health notices related to the following mosquito-transmitted diseases:
Zika Virus

Chikungunya Virus

Frequently Asked Questions

  • Can West Nile Virus be treated?
    There is no specific treatment for WNV infection. In milder cases, people experience symptoms such as fever and aches that pass on their own; although, illness can last weeks to months. In serious cases, a person may have to be hospitalized and given supportive treatment (e.g. intravenous fluids, help with breathing), along with nursing care. Currently there is no vaccine for WNV, but the CDC is working with partners to develop one.
  • What’s the risk of getting very sick from West Nile Virus?
    People over 50 are at higher risk to get severe illness; although, all ages can become seriously ill. Being outside without taking precautions means you are at risk; the more time you spend outdoors
    (working or playing) the more time you are exposed to bites from an infected mosquito. Risk of virus transmission through medical procedures is very low. Pregnancy and nursing DO NOT increase risk of becoming infected with WNV.
  • Can animals be infected with West Nile Virus?
    Yes. WNV can infect just about any animal, including dogs and cats — however, the good news is they rarely, if ever, become sick from the virus. Horses appear to be the only domestic animal adversely affected by WNV, and there is a vaccine available.
  • Do all mosquitoes carry West Nile Virus?
    No. In this area, it is primarily transmitted by members of the Culex species, and only females bite humans. Typically, this mosquito flies short distances (often much less than a mile) to feed. Adult mosquitoes have a life span of a few weeks during the summer months.