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Title:Impacts of organic and conventional neurotoxic pesticides on a pest and a pollinator in almond agroecosystems (Prunus dulcis)
Author(s):Dana, Catherine E.
Advisor(s):Berenbaum, May R.
Contributor(s):Harmon-Threatt, Alexandra N.; Spencer, Joseph L.
Department / Program:Entomology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Amyelois transitella
cytochrome P450 monooxygenase
Apis mellifera
Abstract:The navel orangeworm Amyelois transitella (Walker) (Lepidoptera: Pyralidae) is an economic pest on a wide variety of tree fruit and nut crops, including almonds, pistachios, and walnuts in California orchards. Rising demand for these high-value cash crops has led to an increased reliance on synthetic insecticides to reduce damage from this pest. At the same time, consumer interest has risen for organic products, resulting in the development and usage of novel chemical controls, such as spinosyns, derived from natural products, in contrast with conventional pesticides, such as neonicotinoids, synthesized based on natural products. Both spinosyn and neonicotinoid insecticides act on binding sites of the nicotinic acetylcholine receptors. Although used against specific target pests, both spinosyns and neonicotinoids are broad-spectrum insecticides and thus can have non-target effects on beneficial arthropods in agroecosystems, including pollinators. In this study, focused on the almond production system in California's Central Valley, I examined impacts of the synthetic neonicotinoids and the organic spinosyns on the pest navel orangeworm and the managed pollinator Apis mellifera. Chapter 1 describes an examination of the toxicity and mode of detoxification of two neonicotinoids and a spinosyn in navel orangeworm utilizing inhibitors of specific enzyme groups to test for synergistic enhancement of toxicity. The effects of the cytochrome P450 monooxygenase (P450) inhibitor piperonyl butoxide and the glutathione-S-transferase inhibitor diethyl maleate on the toxicity of the insecticides acetamiprid, clothianidin, and spinosad (a natural fermentation product made up of a mixture of Spinosyn A and D) were assessed in a series of bioassays with first instar A. transitella larvae from a laboratory strain (CPQ). An increase in the toxicity of acetamiprid and spinosad by piperonyl butoxide implicates P450s in the detoxification of at least some representatives of neonicotinoid and spinosyn insecticide classes. However, there were no significant differences in toxicity of the neonicotinoid clothianidin with the addition of either piperonyl butoxide or diethyl maleate. Because P450-mediated resistance to the pyrethroid insecticide bifenthrin has been reported in Kern County, California, determining the range of pesticides metabolized by P450s is critical for making management decisions designed to delay widespread cross- and multiple-resistance acquisition. In Chapter 2, I measured the behavioral responses of free-flying honey bees (Apis mellifera) to the presence of pesticides in a sugar water solution, including neonicotinoids currently or previously used in almond orchards for management of navel orangeworm or other pests. Sugar water feeders containing imidacloprid at 5 ng/mL were more attractive to free-flying honey bees relative to unamended sugar water feeders. No attraction or repellency was seen with acetamiprid at concentrations of 50 ng/mL, 500 ng/mL, and 5 µg/mL. Thus, in semi-field conditions, honey bees may be attracted to and preferentially feed on foods contaminated with a highly toxic pesticide at low concentrations. My findings highlight the need to consider unintended and non-target impacts of using insecticides to control pests in crop settings, such as almond orchards. Growers that use pesticide rotation to avoid resistance or utilize organic products need to consider if there is any overlap in detoxification enzymes used by their target pest and what impacts residues of these different insecticides might have on foraging honey bees on which they rely to pollinate their crop.
Issue Date:2016-07-12
Rights Information:Copyright 2016 Catherine Dana
Date Available in IDEALS:2016-11-10
Date Deposited:2016-08

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