Frequently Asked Questions

I filled out a permission form to allow access to my property, but you never came. What happened?
The one-time landowner permission form is required before we are able to access private property for any TCWP activity. It does not, however, indicate to us your request for service. If you have potential mosquito habitat, adult mosquitoes, or weeds you’d like advice on treating please fill out a service request or call our office at 307.733.8419.

Why haven’t I been sprayed for mosquitoes yet?

There are many reasons why we may not have been to your area to treat for adult mosquitoes (adulticide) with our ULV (ultra low volume) truck spraying. We strive to provide all our services in the most environmentally sensitive way, and adult mosquito control is a “last resort”.  It is much more efficient, effective, and safe to treat mosquitoes at their source with larvicide and that is the mainstay of our control program.  When it does become necessary to adulticide, the following are reasons we may not spray an area:

  1. Trap Counts – All of our control work is based on surveillance data. To determine the need for adulticiding, we set a trap to see how many mosquitoes are in an area. If the number of mosquitoes caught in the trap does not meet minimum action thresholds, we will not spray for adults.
  2. Permission – We must have permission to adulticide from a majority of the landowners in an area in order to treat that area effectively. If there are “no spray” preferences or “no permission on file” for multiple landowners, we will not spray.
  3. Weather – Weather conditions must be optimal for us to have an effective treatment. We spray for adult mosquitoes in the evenings.  If it is too rainy, windy, or even too calm, we cannot spray and will reschedule to the next opportune evening.
  4. Awareness – While we routinely trap adult mosquitoes throughout the County and strive to be aware of conditions throughout our respective territories, we may not always be aware of a localized adult mosquito surge. A single service request (form found here) from a neighborhood will draw our attention to the matter.

How do you control mosquitoes in Teton County?
90% of our time is spent applying a biorational pesticide to control mosquito larvae. We apply a bacterial protein to standing water where mosquito eggs have hatched. As the larvae filter feed in the water column they ingest the protein (which is activated by conditions in a mosquito’s digestive tract and perforates the gut wall) and they gradually die. Sometimes, in areas where we have missed a brood of mosquitoes or cannot access the larval development sites due to National Park or Forest Service restrictions, we apply adulticides by truck-mounted ULV (ultra low volume) sprayers. When large areas require treatment we contract with an aerial applicator that specializes in mosquito control.

How do you know where the mosquitoes develop?
We have many seasons of larval surveillance data from sampling snow pools, marshes, willow bottoms, floodplains, and irrigated pastures and hayfields. However, we are always interested in discovering additional sites. If you know of an area that might be producing mosquitoes, let us know about it using the Service Request option or contact us by phone, 733-8419.

What products do you use to control adult mosquitoes?
TCMA uses both natural and synthetic pyrethrum products. These insecticidal compounds are either harvested directly from or based upon substances in the chrysanthemum plant.

How do you determine where and when to spray for adult mosquitoes?
We have an extensive network of fixed and mobile adult mosquito traps. We use this data along with results of our disease surveillance program to determine the need and scheduling of adult spraying.

How many different kinds of mosquitoes are found in Teton County?
We have currently identified 39 different species of mosquitoes in Teton Co.

Is West Nile virus (WNv) present in Teton County?
West Nile virus has been found in Wyoming since its spread across the country and arrival in this state in 2002. Official WNv results for Teton County include: 1 positive horse each in 2002 and 2005, 1 positive bird in 2004, and 2 positive mosquito samples in 2007. See our West Nile virus page.
Although research is still underway to elucidate the details of the virus’ cycle in North America, the virus has become part of our ecosystem and will likely cycle in severity from year to year, much like other mosquito-borne diseases, namely: Western Equine or St. Louis Encephalitis.

Is Zika virus a threat for Teton County residents?
Similar to dengue and chickingunya, Zika virus is spread readily through mosquito bites. Due to the complex mechanism of the virus spreading within a mosquito and considerable genetic variation between species of mosquitoes, not all mosquitoes are able to transmit all viruses. Luckily, due to geography, Teton County does not currently have the two species of mosquitoes (Aedes aegypti and Aedes albopictus), that effectively transmit dengue, chikingunya, and now, Zika viruses. This means that local mosquito-borne transmission of any of these three viruses is highly unlikely. This does not mean that Teton County residents travelling to any of the areas with Zika outbreaks (see CDC’s website for the most up-to date list) cannot contract the disease and bring it home and potentially spread it through other (non-mosquito) routes (such as pregnancy, transfusion, or sexual contact) that researchers are still determining.

For those traveling, it is important to note that unlike some of the species in Teton County, which are more prevalent in natural areas, prefer to bite when the sun is down, and can be seen and heard coming from a distance, Aedes aegypti is very cryptic, bites at all hours, and resides happily around human habitation. Individuals of this species are acclimated to resting on (usually vertical) surfaces within dwellings and will often not even be noticed when biting. For these reasons, taking precautions against mosquito bites is critical at all times. Wearing loose fitting, long-sleeved shirts and long pants and socks and applying (and re-applying) an effective repellent is crucial. More information on repellents recommended by CDC can be found here.

What does the District do in the winter?
The slower pace of the winter season allows us to catch up on the activities that we lack time for in the summer. These include: analyzing surveillance and control data, updating GIS maps, performing resistance testing, repairing and maintaining equipment, performing water management activities, preparing reports for cooperating agencies, applying for permits, pursuing continuing education, presenting at state, regional and national conferences, updating and delivering educational materials and programs, recruiting and hiring for the next season, pre-treating outlying sites. This is also the time of year when using vacation time is encouraged.