Cardenolide, Potassium, and Pyrethroid Insecticide Combinations Reduce Growth and Survival of Monarch Butterfly Caterpillars (Lepidoptera: Nymphalidae)

Authors

Annie J. Krueger, University of Nebraska-Lincoln
Emily A. Robinson, University of Nebraska-Lincoln
Thomas J. Weissling, University of Nebraska-LincolnFollow
Ana M. Vélez, University of Nebraska-LincolnFollow
Troy D. Anderson, University of Nebraska-LincolnFollow

ORCID IDs

Annie J. Krueger

Emily A. Robinson

Troy D. Anderson

Document Type

Article

Date of this Version

12-2021

Citation

Journal of Economic Entomology 114:6 (December 2021), pp. 2370–2380.

doi: 10.1093/jee/ toab169

Comments

Copyright © 2021 Annie J. Krueger, Emily A. Robinson, Thomas J. Weissling, Ana M. Vélez, and Troy D. Anderson. Published by Oxford University Press on behalf of the Entomological Society of America. Used by permission.

Abstract

The monarch butterfly, Danaus plexippus L., has evolved to be insensitive to milkweed cardenolides via genetic modifications of Na⁺/K⁺-ATPase. There is concern for insecticide exposures near agriculture, with little information on monarch caterpillar toxicology. It is unclear how cardenolide insensitivity may affect the sensitivity of monarch caterpillars to pyrethroid insecticides. Additionally, potassium fertilizers may affect monarch caterpillar physiology and cardenolide sequestration. Here, we investigated the growth, survival, and development of caterpillars exposed to the cardenolide ouabain, bifenthrin, and potassium chloride (KCl) alone and in combination. Caterpillars were either exposed to (1) ouabain from third- to fifth-instar stage, (2) KCl at fifth-instar stage, (3) KCl and bifenthrin at fifth-instar stage, or (4) combinations of ouabain at third-instar stage + KCl + bifenthrin at fifth-instar stage. Caterpillar weight, diet consumption, frass, and survival were recorded for the duration of the experiments. It was observed that 1–3 mg ouabain/g diet increased body weight and diet consumption, whereas 50 mg KCl/g diet decreased body weight and diet consumption. Caterpillars feeding on KCl and treated with 0.2 μg/μl bifenthrin consumed significantly less diet compared to individuals provided untreated diet. However, there was no effect on survival or body weight. Combinations of KCl + ouabain did not significantly affect caterpillar survival or body weight following treatment with 0.1 μg/μl bifenthrin. At the concentrations tested, there were no effects observed for bifenthrin sensitivity with increasing cardenolide or KCl concentrations. Further studies are warranted to understand how milkweed-specific cardenolides, at increasing concentrations, and agrochemical inputs can affect monarch caterpillar physiology near agricultural landscapes.