Document Type

Thesis

Degree

Master of Science

Major

Biology

Date of Defense

7-15-2024

Graduate Advisor

Dr. Aimee Dunlap

Committee

Dr. Aimee Dunlap

Dr. Nathan Muchhala

Dr. Lon Chubiz

Dr. Sonya Bahar

Abstract

In order to feed a growing global population, agricultural practices must utilize pesticides to maintain high yields. Responsible use of pesticides should be based on literature confirming their efficacy and safety. When pesticides are not adequately investigated prior to their release, there can be severe consequences. Many highly effective pesticides, such as the class neonicotinoids, were allowed to be used commercially prior to thorough assessment of their environmental risks, resulting in consequences that largely have fallen to the exposed pollinator populations. To avoid similar outcomes, I tested the popular biopesticide Botanigard which contains Beauveria bassiana, an entomopathogenic fungus previously exposed as contributing to reduced survival and cognitive abilities in honeybees and bumblebees. I am investigating this biopesticide to assess its impacts on the two critical sub-lethal aspects of bumblebee (Bombus impatiens) colonies: learning ability, and division of labor. Using a field-realistic risk assessment design, only a subset of foragers received a topical pesticide dose, and each tested colony received two sets of doses over the experimental period. This mimics the actual circumstances a foraging bee might become exposed to pesticides naturally. Individual learning was assessed using the Free-Moving Proboscis Extension Response (FMPER) test, and colony division of labor was assessed using daily behavioral point samples. This is the first test of its kind investigating both the social and cognitive effects of this particular pesticide on bumblebees at both the colony and individual level. These tests revealed a significant, negative effect on individual scores on the FMPER learning test. As learning is vital to the establishment of pollinator colonies and especially to their ability to forage well and safely, any pesticide that contributes to a learning deficit for pollinating insects should be investigated further. These results, among other notable changes to Botanigard-treated colonies, prove the importance of developing robust and field-realistic pesticide risk assessments that investigate more than simply lethality, and include tests for a variety of sub-lethal impacts.

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