Date of Award


Document Type


Degree Name

Master of Public Health


Health Science and Human Ecology

First Reader/Committee Chair

Mahmood Nikbakhtzadeh


The southern house mosquito, Culex quinquefasciatus, is a vector to many pathogens in Southern California, including West Nile Virus and St. Louis Encephalitis Virus. Immature stages of mosquitoes may be exposed to Roundup®, a frequently used herbicide worldwide, due to surface runoffs or overspraying and subsequent drifting. Previous studies have shown some negative impacts of sublethal doses of Roundup® during the developmental stage of Culex quinquefasciatus, such as physiologic changes and prolonged larval stage or the high mortality of larvae due to exposure to the high doses of glyphosate. This study investigated the effect of intermediate doses of Roundup® (10 mg/l and 100 mg/l) on Culex quinquefasciatus when immature stages are exposed to this herbicide. Experiments were conducted in the Environmental Chambers at CSU San Bernardino at 27 ± 2°C, RH 70 ± 5%, and 12:12 hour Photoperiod.

Results indicated prolongation of the larval period and delays in pupation upon exposure to the above concentrations of Roundup®. The results also indicated that as the dose of glyphosate increased, the yield of adult emergence decreased. Oviposition experiments have shown fewer egg rafts oviposited as Roundup® concentration increased. Another interesting observation was a significant increase in the adult wingspan when the exposure dose at the larval stage was increased from 10 mg/l to 100 mg/l.

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