Impacts of insect growth regulator pesticides on populations of beneficial dung beetles in Pennsylvania agroecosystems

Date of Award


Document Type

Honors Thesis


Biochemistry & Molecular Biology

First Advisor

Jason Smith




Horn flies are a common pest to cattle in agroecosystems resulting in economic losses of hundreds of millions (USD) to farmers annually. Their populations can be controlled through the use of insect growth regulators (IGRs), which act as hormone mimics and therefore, as targeted pesticides that are not broad spectrum. However, as horn flies develop in cattle dung, the use of IGRs also directly impacts a variety of other organisms, notably dung beetles. Dung beetles provide a multitude of services to an ecosystem, and it is therefore vital that their populations not be reduced through the use of IGRs. To assess the effects of IGRs, cattle dung was artificially spiked with methoprene and diflubenzuron and then left in the field for a week to allow colonization to occur. The dung pats were then enclosed in emergence chambers in the lab and collections taken twice weekly of any resultant organisms over the course of ten weeks. All emerging beetles, flies and parasitic wasps were sorted and the beetles identified to genus to analyze the community level effects of the IGRs. Methoprene significantly impacted the Aphodius beetles and some parasitoid wasps, while diflubenzuron resulted in the complete absence of all parasitoid wasps and greatly impacted the flies. Additionally, both IGRs reduced the overall diversity of the emerging dung fauna. This study is among the first to examine how realistic doses of methoprene and diflubenzuron impact the survival and development of non-target species in dung fauna in a holistic field-based study.

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