13 May 2019 Can Indirect Herbicide Exposure Modify the Response of the Colorado Potato Beetle to an Organophosphate Insecticide?
Aigi Margus, Miia Rainio, Leena Lindström
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Organisms live in complex multivariate environments. In agroecosystems, this complexity is often human-induced as pest individuals can be exposed to many xenobiotics simultaneously. Predicting the effects of multiple stressors can be problematic, as two or more stressors can have interactive effects. Our objective was to investigate whether indirect glyphosate-based herbicide (GBH) exposure of the host plant has interactive effects in combination with an insecticide (azinphos-methyl) on an invasive pest Colorado potato beetle (Leptinotarsa decemlineata Say). We tested the effects of GBH and insecticide on the survival, insecticide target genes expression (acetylcholinesterase genes) and oxidative status biomarkers (glutathione S-transferase [GST], glucose-6-phosphate dehydrogenase [G6PDH], glutathione reductase homolog [GR], glutathione peroxidase homolog [GPx], total glutathione [totGSH], glutathione reduced-oxidized [GSH: GSSG], catalase [CAT], superoxide dismutase [SOD], lipid hydroperoxides). We found that exposure to indirect GBH has no single or interactive effects in combination with the insecticide on larval survival. However, prior exposure to GBH inhibits Ldace1 gene expression by 0.55-fold, which is the target site for the organophosphate and carbamate insecticides. This difference disappears when individuals are exposed to both GBH and insecticide, suggesting an antagonistic effect. On the other hand, oxidative status biomarker scores (PCAs of GPx, GR, and CAT) were decreased when exposed to both stressors, indicating a synergistic effect. Overall, we found that indirect GBH exposure can have both antagonistic and synergistic effects in combination with an insecticide, which should be considered when aiming for an ecologically relevant risk assessment of multiple human-induced stressors.

© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Aigi Margus, Miia Rainio, and Leena Lindström "Can Indirect Herbicide Exposure Modify the Response of the Colorado Potato Beetle to an Organophosphate Insecticide?," Journal of Economic Entomology 112(5), 2316-2323, (13 May 2019). https://doi.org/10.1093/jee/toz115
Received: 23 November 2018; Accepted: 4 April 2019; Published: 13 May 2019

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glyphosate-based herbicide (GBH)
interactive effect
Leptinotarsa decemlineata Say
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