Non-target effects of clothianidin on monarch butterflies
Monarch butterflies (Danaus plexippus) frequently consume milkweed in and near agroecosystems and consequently may be exposed to pesticides like neonicotinoids. We conducted a dose response study to determine lethal and sublethal doses of clothianidin using a 36-h exposure scenario. We then quantified clothianidin levels found in milkweed leaves adjacent to maize fields. Toxicity assays revealed LC10, LC50, and LC90 values of 7.72, 15.63, and 30.70 ppb, respectively. Sublethal effects (larval size) were observed at 1 ppb. Contaminated milkweed plants had an average of 1.14 ± 0.10 ppb clothianidin, with a maximum of 4 ppb in a single plant. This research suggests that clothianidin could function as a stressor to monarch populations.
KeywordsAsclepias Danaus plexippus Neonicotinoid Non-target Seed treatment
The authors wish to thank Janet Fergen and Greta Schen for help in laboratory assay preparation, Mike Bredeson and Dr. Chrissy Mogren for ELISA optimization, and Claire Bestul, Marissa Layman, and Cassandra Lewandowski for monarch collection. Stefan Jaronski, Ian Kaplan, Mark Longfellow, John Tooker, Mace Vaughan, and Don Weber improved earlier drafts of this manuscript. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.
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