Evaluation of the role of plant-derived chemicals in mosquito ecology and control

Although blood-feeding behavior in female mosquitoes, required both for reproduction and transmission of disease pathogens, has been extensively studied, plant-feeding is an essential element in the life histories of most mosquito species. For these species, adults of both sexes seek out and depend on floral nectar. Moreover, the larvae of the majority of mosquito species consume dead decaying plant material as a principal source of nutrition. Thus, throughout their lives, mosquitoes encounter phytochemicals. The ecological and physiological impacts of these phytochemicals are thus consequential but are poorly understood. In this dissertation, I conducted laboratory bioassays to evaluate the role of plant-derived chemicals on mosquito ecology and control. Chapter 1 provides background information about mosquito and plant interactions, outlining the ecological significance of nectar phytochemicals on foraging pollinators, pointing out the knowledge gap for mosquitoes, and the potential of plant-derived products including plant oils as promising safe and sustainable tools for mosquito control. In Chapter 2, I conducted laboratory assays to investigate the lethality and repellency of edible plant oils against the container-dwelling mosquito, Aedes aegypti. I demonstrated their lethal potential against the larvae, the role of the oils in delaying larval development, and interference with oviposition site selection by gravid females. Moreover, I showed that the linoleic acid component of the oils contributes to their insecticidal activity. In Chapter 3, I performed laboratory assays to assess the effect of the nectar phytochemicals, caffeine, p-coumaric acid and quercetin on sugar-feeding behavior, La Crosse virus (LACV) infection, and key life-history traits such as longevity and fecundity of the Asian tiger mosquito, Aedes albopictus. Dietary p-coumaric acid, and quercetin resulted in extended female Ae. albopictus lifespan. Caffeine ingestions led to reduced sugar consumption and enhanced fecundity of the female mosquitoes. Additionally, caffeine consumption resulted in reduced LACV susceptibility in female mosquito midguts (Appendix B). In Chapter 4, I used RNA sequencing (RNA-Seq) analysis to characterize the transcriptional profile of female Ae. albopictus adults consuming sucrose diets containing p-coumaric acid or quercetin. These findings revealed that, as antioxidants, p-coumaric acid and quercetin affect gene expression in mosquitoes, with the former showing a stronger effect; as well their lifespan extending-capacity is related to regulation of expression of genes related to xenobiotic metabolism and longevity. Collectively, these studies demonstrate that phytochemicals affect key ecological and behavioral processes in Aedes mosquitoes and offer promising leads for novel approaches to sustainable management of these medically important insect pests.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Entomology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2020

Author dc:creator

• Njoroge, Teresia Muthoni

Contributors dc:contributor

• Berenbaum, May
• Stone, Christopher
• Schuler, Mary
• Allan, Brian
• Calla, Bernarda

• Mosquitoes
• plant-derived chemicals
• mosquito control
• ecology
• gene expression

Statement dc:rights

• Copyright 2020 Teresia Njoroge

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/108704

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/108704