In addition to considerable data collection through our robust surveillance efforts, The District is continuously engaged with applied research to help answer important operational questions. This helps the District to better understand targeted populations, identify problems, and improve management strategies.
Areas of research include the evaluation of new commercial herbicide product efficacy in our local systems, invasive species management methodologies, local mosquito ecology and population dynamics, vector-borne disease prevalence, insecticide resistance, and larvicide and adulticide application efficacy. Research projects are conducted in both the field and our laboratory.
Cheatgrass management in Teton County began in 2011 when the invasive annual grass began expanding along roadsides, levees, the National Elk Refuge, and up south facing hillsides around the valley. A three year, $50,000/year grant was received from the Wyoming Wildlife and Natural Resources Trust to assist with treatment. At the time it was believed that cheatgrass could be adequately controlled utilizing Imazapic. At this time, no aerial application methods were approved on National Forest lands, where most of the infestations were located.
Following the three year project, cheatgrass was declared by Teton County Weed and Pest so that District funds could be utilized for the continued management. Over the next 4 years, the management of the species in the locations that were infested proved to be unsustainable.
In 2017, with the process underway to approve aerial application of herbicides on National Forest Lands, and an alternative herbicide option on the market, TCWP proposed a pilot project treating cheatgrass aerially, on East Gros Ventre Butte in the Town of Jackson. This project, funded again by the WWNRT, treated around 300 acres of cheatgrass with monitoring plots established to evaluate the effectiveness of the two herbicide choices.
Monitoring of the pilot project treatments took place yearly during the summers of 2018-2020. During which time, funding was obtained via various granting organizations to scale the project up to include most of the large cheatgrass infestations within Teton County. In order for this project to take place, the missing piece was an Environmental Analysis and National Environmental Policy Act (NEPA) to authorize the application of herbicides aerially on the Bridger Teton National Forest. Once this was in place, the 4,365-acre project was initiated. Through the analysis of the monitoring transects that were part of the pilot project in 2017, it was determined that the best herbicide of choice was Indaziflam, and it was utilized for the majority of the 2020 project.
The residual effects of the herbicide used has allowed for the areas that were treated to maintain control over the last two years. Data has shown that control usually breaks between year three and year 4 after initial treatment, and cheatgrass seed bank viability dramatically decreases after year 5. With this information, a follow up treatment has been planned for the summer of 2023. With this planned treatment, cheatgrass seed viability will have, for the most part, be exhausted in the areas treated. These previously infested areas will have been rehabilitated back to the pre-infested state, and future treatment will depend on how resilient these areas are to future reinfestation.
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The District routinely investigates the insecticide susceptibility of different mosquito populations throughout the county to monitor for resistance. This is to ensure that the products we may be using are effective in the field. When resistance is detected, the District conducts further research to determine the degree, spatial prevalence, and mechanisms of resistance using standardized methodologies.
In 2022, preliminary evidence of resistance was detected in a population of the WNV vector species Culex tarsalis. In 2023, the District will be researching this population further to confirm resistance and investigate any resistant mechanisms.
Sometimes when mosquito populations are susceptible to a product, there are other factors that may reduce its efficacy such as equipment or environmental factors, which may impact control. In 2023, the District will be conducting a field study to determine the effectiveness of larvicide drone applications in areas of continual flooding.