Entomology, Department of
First Advisor
Troy D. Anderson
Date of this Version
4-2020
Abstract
One outstanding threat to the honey bee, Apis mellifera L., is the unintended exposure of these pollinators to agricultural pesticides. Anthranilic diamides, such as chlorantraniliprole, work in target pests through activation of the ryanodine receptor causing rapid feeding cessation, lethargy, paralysis, and eventual death. Chlorantraniliprole exhibits low acute toxicity to honey bees but relatively little information exists regarding effects of chlorantraniliprole exposure beyond mortality. The acute toxicity and metabolic detoxification enzyme activities following oral exposure were determined in the honey bee and the model crop pest, the fall armyworm (Spodoptera frugiperda, J.E. Smith). Additionally, chlorantraniliprole effects on honey bee survival, locomotor activity, and two immunological parameters following immune challenge were observed in laboratory bioassays. After a 72 h exposure, neither the technical grade or three formulated products of chlorantraniliprole were observed to be acutely toxic to honey bees at solubility limits or maximum recommended label concentrations, respectively. However, all treatments with chlorantraniliprole were acutely toxic to fall armyworm. Honey bees receiving a 4 h exposure of all chlorantraniliprole treatments survived similar to untreated controls although honey bees receiving a 72 h exposure had significantly decreased survival over 30 d. The locomotor activity of honey bees receiving a 4 h exposure of chlorantraniliprole had decreased locomotion in one formulation treatment group, but walking activities returned to control levels the following day. In contrast, walking distance was significantly decreased at each time point in honey bees receiving chlorantraniliprole treatment for 72 h. Following determination of cytochrome P450 monooxygenase (P450), general esterase (EST), and glutathione S-transferase (GST) activities in both insect species, P450- and GST-mediated detoxification appears likely in the fall armyworm, while enzyme activities were not altered in honey bees in a manner consistent with enhanced detoxification. After injection with a viral or bacterial pathogen, honey bees pre-exposed to technical-grade chlorantraniliprole and provided a bacterial immune challenge had increased phenoloxidase activity, which suggest an alteration of this immune cascade. This study provides additional information regarding sublethal effects of an increasingly used compound in a beneficial species and, in turn, serves to bridge knowledge gaps related to chlorantraniliprole exposures and pollinator health.
Advisor: Troy D. Anderson
Comments
A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Entomology, Under the Supervision of Professor Troy D. Anderson. Lincoln, Nebraska: May 2020
Copyright 2020 Jennifer R. Williams