Date of Award

Summer 2020

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

School

Biological, Environmental, and Earth Sciences

Committee Chair

Dr. Donald Yee

Committee Chair School

Biological, Environmental, and Earth Sciences

Committee Member 2

Dr. Jake Schaefer

Committee Member 2 School

Biological, Environmental, and Earth Sciences

Committee Member 3

Dr. Wendy Varnado

Abstract

Larvicides are chemicals used to kill juvenile mosquitoes. When applied to an area, other aquatic organisms are exposed to these chemicals. The removal or impairment of top insect predators could be beneficial to mosquito populations once harmful pesticide levels dissipate. Two common larvicides were examined: growth regulators (IGRs) and surface films (SFs). The goal of this project was to determine if larvicides harm mosquito predators common to southern Mississippi. I surveyed aquatic sites before and after IGR and SF treatments, and then compared changes in insect community structure. Community evenness was lower in SF treated habitats. When analyzing prey taxa only, evenness and diversity changed in control treatments, which suggests that differences measured were due to other environmental factors, not larvicide presence. I examined lethal and behavioral effects of IGRs and SFs on predatory insects. Surface films were lethal to Laccophilus adults (Coleoptera: Dytiscidae) at recommended and high concentrations. Dragonfly nymph location preference in aquariums varied between SFs and IGRs. Laccophilus larvae in IGRs spent more time moving and eating compared to SFs. Behavioral differences were among combined concentrations in both larvicide treatments, not within their respective concentrations and controls. Experiments were conducted to determine IGR and SF effects on the mosquito-regulating ability of predaceous insects. Treated predators were placed in mesocosms containing mosquito larvae. Mosquito survival was quantified by capturing emerging adults. There were no differences in emergence among all treatments. Implications of the findings from this thesis, similarities to past research, and suggestions for future work are discussed.

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