Date of Award:

5-2021

Document Type:

Dissertation

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Ricardo Ramirez

Committee

Ricardo Ramirez

Committee

James Strange

Committee

Theresa L. Pitts-Singer

Committee

Earl Creech

Abstract

With native pollinator species on the decline and the honey bee (Apis mellifera L.) industry suffering, it is imperative that we understand the impacts of agricultural practices on pollinators. The blue orchard bee, Osmia lignaria (Megachilidae), is an important alternative pollinator of commercial orchards. Osmia lignaria are solitary, cavity nesting bees with a wide distribution across North America. This species and other solitary, cavity nesting bees experience different routes of pesticide exposure than social pollinators, such as colony-dwelling bumble bees and honey bees. Chapter I focuses on routes of pesticide exposure experienced by cavity-nesting bees, incorporating the relative importance of environmental contamination due to pesticide chemical properties. Exposure routes described are larval ingestion, adult ingestion, contact, and transovarial transmission. In Chapter II, to investigate the effect of pesticides on solitary, cavity nesting bee larvae and develop a methodology for larval pesticide testing, a laboratory bioassay was conducted using O. lignaria. Two pollen types (apple and almond), two provision compositions (homogenized and intact natal), and four agrochemicals (acetamiprid, boscalid/pyraclostrobin, organosilicone, and dimethoate) were delivered at different does and examined for effects on larval development times and mortality before larvae began to spin cocoons. Mortality varied by provision type and treatment. All larvae survived to cocoon initiation when only water (control) was added to provisions of all types. When the intact natal provision was used, there was no or low mortality across agrochemical treatments. Mortality in the homogenized provision was highest when acetamiprid was the treatment, especially for provisions made from almond pollen. In the third chapter, the impacts of pesticide sprays on adult O. lignaria foraging behavior was investigated with a field cage study conducted in Poplarville, MS. The fungicide caused hyperactive behavior with low mortality, whereas individuals exposed to the insecticide showed signs of stress and experienced high mortality rates.

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