UC Riverside

Many countries are utilizing reclaimed wastewater for agriculture because drought, rising temperatures, and expanding human populations are increasing water demands. Unfortunately, wastewater often contains biologically-active, pseudopersistant pharmaceuticals, even after treatment. Runoff from farms and output from wastewater treatment plants also contributes high concentrations of pharmaceuticals to the environment. However, there is a lack of information on how these pharmaceuticals could affect insects living in these environments, the insects’ microbial communities, and possible pest management applications. The overall goal of this dissertation is to form a base groundwork to assess the effects of common pharmaceuticals on important insect pests in different feeding guilds. The findings of this research demonstrate a wide range of effects from insect to insect with some unexpected effects.

Culex quinquefasciatus larvae reared in water contaminated with certain pharmecuticals were found to have increased developmental time, susceptibility to Bacillus thuringiensis subsp. Israelensis, and altered microbial communities. Within control treated C. quinquefasciatus, the predominant families of bacterial symbionts change with each larval instar despite consistent diets and rearing conditions. This trend was not observed the antibiotic or the mixture treatments. Interestingly, the mixture treatments had greater richness and evenness compared to antibiotic alone treatments, possibly due to the other contaminants facilitating growth of different bacteria.

Female Megaselia scalaris flies showed no oviposition preference for treated or untreated diets. Larvae exposed to certain pharmaceuticals in artificial diets showed increased mortality, signs of slowed development, especially in females, and altered sex ratio. There was an overall effect of treatment on the flies’ microbial communities; notably, caffeine fed insects displayed higher microbial variability.

Trichoplusia ni showed increased developmental time and mortality when reared on artificial diets containing antibiotics, hormones, or a mixture of contaminants. Mortality was also increased when T. ni were reared on tomatoes grown hydroponically with the same concentrations of antibiotics. Microbial communities of T. ni changed substantially between developmental stages and when exposed to CECs in their diets.