Date of Award
2024
Degree Type
Thesis
Degree Name
Master of Science in Biological and Environmental Sciences (MSBES)
Department
Plant Sciences and Entomology
First Advisor
Thomas N. Mather
Abstract
Ticks are vectors of diseases and are a significant public health concern in the United States. Over the last several decades, two medically important species, the blacklegged tick (Ixodes scapularis) and the lone star tick (Amblyomma americanum) have rapidly expanded their geographic ranges. As the number of ticks increase, so does the chance for disease incidence - especially in areas where ticks were not previously present. Together, these two species carry multiple pathogens that can cause serious diseases including Lyme disease, ehrlichiosis, babesiosis, anaplasmosis, and several viral infections.
One of the most common methods for preventing tick bites and tickborne diseases involves using acaricides, chemicals used to kill ticks and mites, to treat outdoor areas like residential yards. Due to several factors including phenology, differences in tick behavior, and cost, it can be difficult for the public to properly control for ticks, even if they are attempting to do so. Additionally, surveys have found that the public is generally reluctant to treat their properties with pesticides (Beck et al. 2022). Many respondents claimed they would be more willing to consider less toxic, environmentally friendly products if effective and available.
In recent years, interest in developing environmentally friendly pesticides has increased due to increasing resistance to synthetic chemicals, contamination of agriculture and livestock, negative biological and environmental effects, and real or perceived harm to non-target species, especially pollinators. Because of this, many minimum risk pesticides (MRPs) made with ingredients like plant extracts and essential oils have been created and made commercially available. These MRPs are exempt from registration by the United States Environmental Protection Agency (EPA) under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) because ingredients were determined to pose little risk to humans or the environment. As a result, many commercially available products have not been evaluated to determine if they actually kill ticks, and consumers have no ability to make informed decisions about the products they are purchasing to protect themselves from ticks.
In 2020, the EPA formally registered an active ingredient (a.i.) named nootkatone, a biopesticide (or pesticide derived from nature). The United States Centers for Disease Control and Prevention (CDC) partnered with Swiss company Evolva to manufacture nootkatone-based insecticides and repellent products for public use. However, testing is still needed for these nootkatone products (NootkaShield), and the results must be submitted to the EPA for review before they can become commercially available for tick control.
At the University of Rhode Island, a collaboration between Dr. Matthew Kieswetter and Dr. Steven Alm resulted in the synthesis of several novel fluvalinate derivatives (KP products), created by Kassie Picard, PhD. A round of lab assays found two of the compounds to have low toxicity toward honeybees and high toxicity toward blacklegged ticks. There is potential for further development of these compounds as bee-friendly acaricides, but additional lab testing and field testing is needed to determine whether the KP products are truly effective for tick control.
In studies reported in this thesis, both the NootkaShield and KP products were evaluated against nymphal blacklegged ticks during the summers of 2023 and 2024 to determine their tick-killing efficacies. Three NootkaShield products were also evaluated against nymphal lone star ticks in summer 2024. KP products were first evaluated in lab bioassays to determine LC50 values, the dosage needed to kill 50% of a group of test organisms. These values were used to determine the concentrations of KP products to be tested outdoors. Field trials using a micro-plot arena system were used to evaluate the chosen KP and NootkaShield products. The micro-plot system was altered for nymphal lone star tick trials to accommodate for the species’ more aggressive host-seeking behavior.
Overall, there were promising results from both studies, specifically for products containing 10% nootkatone and the low dose of KP-41. Based on our results, we recommend these products be developed further for public use to prevent against ticks and tickborne diseases. Further testing is needed to verify the products’ high efficacies and to account for variation in efficacy across years.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Recommended Citation
Sengsourinho, Chantal, "EVALUATION OF ENVIRONMENTALLY FRIENDLY PRODUCTS FOR USE AGAINST IXODES SCAPULARIS AND AMBLYOMMA AMERICANUM TICKS (ACARI: IXODIDAE)" (2024). Open Access Master's Theses. Paper 2540.
https://digitalcommons.uri.edu/theses/2540