2023 End of Year Report


Teton County Invasive Species met their match in 2023 with our committed team! All members of our team worked tirelessly in the field, on the Snake River, in the classroom, with community outreach programs, at your homes and properties, and coordinated with volunteers and partner organizations. That is a LOT of work! Enjoy highlights from our 2023 Year End Report and read the report in full from the download link above.

Mosquito Program

TCWP utilizes Integrated Mosquito Management (IMM) to prevent mosquitoes and the diseases they spread. In Teton County, Culex tarsalis is the species of mosquito with the greatest potential to spread diseases to humans, livestock and wildlife, and the TCWP IMM program centers on preventing and monitoring for this species.

Efficacy Testing:

Flood water irrigation is one of the primary mosquito breeding habitats in Teton County. Low lying areas in fields are shallow and stagnant, which provides warm water for mosquitoes to reproduce. During peak season, mosquitoes can mature from egg to adult in as little as 7 days in these areas. Because flood irrigation is extensive in Teton County, residual and extended release products are essential to conducting effective management. In 2023, TCWP began efficacy testing on an additional product that is labeled to provide mosquito control for up to 42 days and can be applied up to 28 days prior to flooding.

Pesticide Resistance Testing:

TCWP conducts pesticide resistance testing to monitor for pesticide resistance in mosquito populations in Teton County as a part of the IMM program. Larval samples are collected in the field, reared in the TCWP lab, and tested against susceptible lab colonies.

Bottle Bioassay

Bottles are coated with different insecticides, mosquitoes are placed in the bottles, bottles are observed at short intervals for two hours. While the bottles are observed for two hours, diagnostic time, or the time in which bottles should have 100% mortality, for pesticides varies. The diagnostic times for permethrin and malathion are 30 and 45 minutes respectively. Colonies and field samples are tested with both malathion and permethrin to determine the rate of mosquito death.

Microplate Assay

Mosquitoes are processed with reagents that can be read by a spectrometer to determine presence/absence and quantity of enzymes that cause resistance. Microplate assays can help determine what type of resistance is present in mosquito populations. These assays are complete for 2023, and the data are being analyzed.

Invasive Plants

Despite a rainy start to the season, TCWP seasonal crew members spent 3,301.76 hours managing invasive plants this year. TCWP crews work on public lands throughout the county. TCWP coordinates with federal, state, and county land management agencies and organizations to prioritize areas for treatment or to supplement work conducted by the managing entity.

Early Detection and Rapid Response (EDRR) is a management strategy that aims to prevent the establishment or widespread infestation of invasive plants. EDRR requires extensive monitoring for new invasive species and new locations of invasive plants already within the area; any invasive plants that are located are treated or removed as quickly as possible to prevent establishment.

Each year TCWP hires one or two seasonal crew members to serve as EDRR leads. These crew members spend the entire summer season monitoring and treating known EDRR locations on public and private land throughout Teton County. This year 1256 EDRR locations were monitored, and 523 of those locations were found to have no live plants. Monitoring will continue for most of these locations, but TCWP considers a species to be eradicated from a location finding no live plants for 5 continuous years. This year eradication was declared at 89 locations.

Snake River Project:

The Snake River Project was launched by the Jackson Hole Weed Management Association (JHWMA) more than 20 years ago after ltcedar was found on the Snake River in 2001. Each year TCWP and the JHWMA monitor for invasive plants on the Snake River from the Jackson Lake Dam to Palisades Reservoir. Crews float the river and stop on islands and gravel bars along the way. EDRR species are monitored, treated, and removed to maintain this valuable resource.

Working Dogs for Conservation:

In 2020, TCWP and the JHWMA partnered with Working Dogs for Conservation to help locate additional saltcedar and perennial pepperweed locations. This year the canine teams located 67 perennial pepperweed points, primarily along the Gros Ventre River. Given the size of the points found, these locations may be the seed source for the perennial pepperweed points that have been found downstream and along the Snake River.

TCWP staff and crew visited each of the locations identified by the canine and handler teams. Treatments and removal were conducted, and the sites will be visited each year until the plants have been eradicated at these locations.

Aerial Applications

The topography and land uses in Teton County provide unique challenges for managing invasive plants and mosquitoes. Managing invasive plants on steep slopes is both difficult and dangerous, and managing mosquitoes in extensive flood irrigation requires more days of crew time than are available.

Recent technological advances in pesticides and equipment allow TCWP staff to utilize aerial application in management programs. Aerial application provides more consistent pesticide application, is safer for TCWP staff and crew, and allows for more timely management.

Unmanned Aircraft Systems (Drones)

TCWP has utilized Unmanned Aircraft Systems (UAS), also called drones, in several locations for the last few years. However, this year TCWP staff utilized UAS in as many locations as possible. UAS allow staff to safely conduct invasive plant management on steep slopes. They also allow for large-scale treatment of mosquito larva in areas that are inaccessible by truck or UTV. By utilizing UAS in these areas, seasonal crew members are available to work in higher priority areas (e.g. less dense infestations or mosquito populations) allowing us to protect additional areas.

Cheatgrass Project Round 2

The Jackson Hole Weed Management Association (JHWMA) and TCWP conducted the second round of treatments for the Cheatgrass Management Program in August 2023. More than 4700 acres were treated by helicopter and UAS throughout the valley.

Cheatgrass (Bromus tectorum)

Cheatgrass is a highly invasive, non-native annual grass with a quick growing life cycle that gives it a competitive advantage over native vegetation. It readily outcompetes native forbs and grasses for water and nutrients quickly creating dense monocultures. While cheatgrass is a prolific seed producer, its seeds are only viable in the soil for about 5 years.

Rejuvra (indaziflam)

Rejuvra is a pre-emergent herbicide that inhibits production of cellulose. After application, the herbicide moves into the top few inches of soil where it remains viable for three years. Rejuvra impedes development of germinating plants and should be applied by late August to prevent fall flushes of cheatgrass. While germination of native annuals is impacted while Rejuvra is present in the soil, native perennials are not impacted by these treatments.

The treatments conducted this year are, hopefully, the final round of large-scale aerial treatments that began in 2017 with a small pilot program on state land on East Gros Ventre Butte. Through the pilot program TCWP tested the efficacy of aerial applications of Plateau (imazapic) and indaziflam (sold as Esplanade at the time) with indaziflam having less off-target impacts. The first large-scale treatment of Rejuvra by helicopter occurred in 2020. With the treatment this year, cheatgrass should be removed or greatly reduced in treated areas by 2026.


K-12 Programs

TCWP staff work with Teton County School District teachers to teach children about invasive species and mosquito management while also providing teachers with the option to utilize TCWP expertise to cover Wyoming curriculum standards. Since 2018, programs have centered on second through fifth grade. This year, TCWP staff capitalized on the success and foundation built in previous programs to expand into a new high school program. TCWP staff conducted 133 hours of instruction reaching 795 students.

Volunteer Program

The Jackson Hole Weed Management Association (JHWMA) partners launched a new coordinated volunteer program this year. This program capitalized on the existing volunteer bases from JHWMA partner organizations reducing the need to advertise for and solicit new volunteers. Additionally, TCWP worked directly with youth organizations that require or encourage community service hours. Each organization adopted an area to provide continued management. TCWP and the Bridger-Teton National Forest crews and technicians supplemented manual removal efforts with herbicide treatment of rosettes.

Landowner Services

TCWP staff provide landowners and residents with a variety of services for invasive plant and mosquito management. Staff conducted more than 25 in-person consultations and mapped and created management plans for more than 275 acres.

2023 also brought a relaunch of the TCWP website (tcweed.org). With the goal of providing residents with easy access to information about TCWP programs and management options that is both easy to understand and scientifically accurate, TCWP staff completely rebuilt the website. The new live chat function proved successful in providing quick responses to simple questions freeing up staff to spend more time on complex questions.

Neighborhood Advocate Program

Many landowners and residents are managing invasive plants on their properties or working with TCWP to manage mosquitoes, but invasive plants and mosquitoes do not recognize property lines. TCWP launched a new Neighborhood Advocate Program to empower individuals to provide accurate information about TCWP programs and how to manage invasive plants and/or mosquitoes on their property. The Neighborhood Advocate Program provides Advocates with information packets that can be handed out to friends and neighbors. These Advocates serve as a contact point for TCWP to provide timely updates throughout the season.

Cost-Share Programs

TCWP offers several programs to assist landowners and residents with the cost of managing invasive plants.

Herbicide Cost-Share:

TCWP continues to provide a 50% cost-share on the sale of select herbicides. Program participants must be a landowner or resident in Teton County, and the herbicide must be utilized for listed species. This year 160 individuals took advantage of this savings.

Invasive Plant Cost-Share Reimbursement Program:

After the successful launch in 2022, TCWP provided the reimbursement program again in 2023. Landowners must reenroll in the program each year, but no additional paperwork is required. TCWP staff conduct informal follow ups to ensure that management is occurring and is effective.

Species of Concern

Hard Ticks

Worldwide mosquitoes kill more people than any other animal through vector-borne diseases, but in Teton County, ticks are the primary vector for many diseases that impact humans, wildlife, livestock, and pets. Ticks in the hard tick, family are adept at spreading diseases like Rocky Mountain Spotted Fever, Lyme disease, and many others.

Wyoming is home to three tick species of medical or veterinary significance. Additional species, both native to the US and invasive in the US, have been documented in Wyoming or neighboring states. Each of these species is capable of carrying a variety of diseases.

Bulbous Bluegrass

Bulbous bluegrass has been slowly spreading in Teton County for several years. TCWP staff have monitored this species to ensure that it did not spread into vulnerable areas while awaiting an effective management tool. However, with the introduction and availability of the herbicide Rejuvra, bulbous bluegrass can now be effectively controlled by land managers.

New Threats


The invasive grass phragmites (Phragmites australis) was located by a seasonal crew member late this summer. This is the first known occurrence of this species in Teton County.

Our Staff and Crew

The Teton County Weed and Pest staff and crew rallied together launching new programs and expanding others throughout the 2023 summer season to meet the needs of residents and visitors in Teton County.

We had an outstanding team this year with 14 seasonal crew members that brought field experience from across the country and new perspectives. They helped conduct vital mosquito testing and completed invasive plant management field work. Two full time staff were hired this season, as well. We couldn't do this work without them!

Thank you to our community for being such amazing advocates of this tireless work and being so diligent in helping us spread the important message of invasive species management! We can hardly wait for the work to start in 2024! 

- The Teton County Weed and Pest Team