Semester of Graduation

Summer 2024


Master of Science (MS)



Document Type



Culex quinquefasciatus Say and Culex pipiens Linnaeus, are primary vectors of West Nile Virus (WNV) in the United States and are medically important because of their anthropophilic relation to humans. While these species are similar in their role of WNV transmission, they differ in geographic distributions and habitats, seasonal activity levels, and climates. Controlling these species challenges integrated mosquito management (IMM) practices because both are pervasive in areas of standing water and can overwinter. This study investigated the cold response of Cx. quinquefasciatus and Cx. pipiens and aimed to determine whether the bacterium, Pseudomonas fluorescens had the potential to reduce cold tolerance in these mosquito species.

Pseudomonas fluorescens, an ice-nucleating bacterium, catalyzes the formation of ice crystals on the surface of its cells and has reduced cold tolerance in stored grain insect pests. Insects that normally overwinter, do not survive at temperatures above freezing when treated with these bacteria. Throughout the fall and winter seasons in the U.S., where there is limited or completely reduced Culex mosquito activity, using an ice-nucleating bacterium as a microbial insecticide and late-season treatment might be beneficial at reducing populations of spring mosquitoes. Pseudomonas fluorescens may have the potential to reduce a mosquito’s tolerance to cold and induce freezing at temperatures they would normally survive. In this study we evaluated cold tolerances of Culex mosquitoes by measuring their supercooling points and chill coma recovery times. Topical bioassays with high and low doses of P. fluorescens did not show significant reduced cold tolerance in Cx. quinquefasciatus and Cx. pipiens, however, blood-fed females of both species and all treatments showed a greater tolerance to cold exposure compared to sugar-fed females. Also, we saw no significant difference in the cold tolerance between species in individuals topically applied with P. fluorescens and untreated individuals. Our results suggest that blood-meal digestion and the accumulation of extra protein, fat body production, and lipid reserves via the blood-meal may contribute to cold tolerance in Cx. quinquefasciatus and Cx. pipiens. Investigation into the mechanism of ice-nucleation in mosquitoes is needed to further study the use of P. fluorescens as a potential microbial insecticide.



Committee Chair

Healy, Kristen

Available for download on Monday, May 03, 2027

Included in

Entomology Commons