Date of Graduation

12-2018

Document Type

Thesis

Degree Name

Master of Science in Entomology (MS)

Degree Level

Graduate

Department

Entomology

Advisor

Neelendra K. Joshi

Committee Member

David J. Biddinger

Second Committee Member

Nicholas J. Seiter

Third Committee Member

Cammy D. Willett

Keywords

Acute Contact Toxicity, Blue Orchard Bees, Honey Bees, Neonicotinoids, Premix Insecticides, Pyrethroids

Abstract

This work investigates ecotoxicology of new insecticide mixtures to Apis and non-Apis bees. Previous studies have demonstrated the acute and sub-lethal toxicity of individual active ingredient insecticides to honey bees and to a lesser extent non-Apis bees. However, the contact toxicity of formulated premix insecticides containing multiple active ingredients to bees has not been thoroughly assessed. To address this void, laboratory studies simulating exposure to four premix insecticides under different field-realistic scenarios were conducted for two bee species.

Honey bee, Apis mellifera (Linnaeus) contact exposure was examined by simulating three scenarios: (1) when bees continuously forage in a field and are directly exposed to insecticides when they are being applied in that field; (2) when bees are exposed to insecticide sprays while passing through a field; and (3) when bees forage through a field in which insecticides were applied during the previous day. Insecticides comprised of neonicotinoid and pyrethroid chemistries were found to be the most toxic, and induced rapid onsets of mortality, while those comprised of diamide, molting hormone agonist and spinosyn chemistries were relatively less toxic, inducing a slower onset of mortality. At 96-hours, overall high mortality was observed for all treatments, thereby indicating the high acute toxicity of these insecticide mixtures to honey bee foragers.

Like honeybees, blue orchard bee, Osmia lignaria (Say), contact exposure was examined by simulating (1) when male and female bees are foraging in an orchard and come into spray-contact with premix insecticides, and (2) when male and female bees come into contact with individual active ingredient insecticides or their 1:1 binary combination. Similar to honey bees, insecticides comprised of neonicotinoid and pyrethroid active ingredients posed the highest toxicity and most rapid onset of mortality for blue orchard bees, and insecticides comprised of diamide, molting hormone agonist and spinosyn chemistries had somewhat lower toxicity, but with more gradual mortality onset. High mortality resulted at 96-hours for all treatments, thereby indicating the high acute contact toxicity of these insecticides. These results will help to improve the current risk assessment framework for laboratory-based insecticide safety trials on bees.

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