Entomology, Department of
First Advisor
Ellis Johnson
Date of this Version
12-2021
Abstract
The yellow fever mosquito, Aedes aegypti L., is among the most important insects as it pertains to public health. It vectors several health-endangering pathogens, including yellow fever, dengue fever, chikungunya, and Zika viruses. Insecticides are among the most effective tools used to manage mosquito populations however, their efficacy to manage mosquito populations is being threatened by insecticide resistance. This ongoing threat warrants new chemical strategies to reduce or incapacitate a mosquito population capable of pathogen transmission. Plant essential oils are candidates for identifying novel management tools for disease-vectoring arthropods. Commercially, essential oils have been used for pharmaceuticals, flavoring, fragrances, cosmetics, and additives for arthropod repellents. These compounds have been suggested to have potentially useful bioactive compounds against insects. This study aimed to identify the volatile phytochemicals found in the oil of Melaleuca cajuputi and examine the larvicidal and adulticidal activity, repellent, and deterrent effects, and ovicidal activity of cajeput oil phytochemicals to pyrethroid-susceptible (Rockefeller or Rock) and -resistant (Puerto Rico or PR) strain of Ae. aegypti. Cajeput VOCs demonstrated effective larvicide activity to Rock while PR displayed greater tolerance to VOC treatments. Cajeput oil and eucalyptol effectively increased cyclic adenosine monophosphate in treated mosquitoes. Phentolamine reduced toxicity of cajeput VOCs. Results show evidence for octopamine receptors to be a potential target site for cajeput VOCs. Cajeput oil VOCs displayed spatial repellency, contact deterrence, and oviposition deterrence against Ae. aegypti. PR mosquitoes had reduced behavioral responses to cajeput VOCs comparable to Ae. aegypti orco5 mutants. Cajeput oil was comparable to DEET as a spatial repellent, and it offers potential to deter pyrethroid-resistant mosquitoes. Further investigations found cajeput VOCs to have greater efficacy at reducing PR mosquito via ovicidal activity. We concluded that cajeput VOCs have potential to be effective tools at reducing mosquito populations as well as providing personal protection from Ae. aegypti.
Adviser: Troy D. Anderson
Comments
A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Entomology, Under the Supervision of Professor Troy Anderson. Lincoln, Nebraska: December, 2021
Copyright © 2021 Ellis J. Johnson