Learning impairment in honey bees caused by agricultural spray adjuvants

Timothy J. Ciarlo, Christopher A. Mullin, James L. Frazier, Daniel R. Schmehl

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

Background: Spray adjuvants are often applied to crops in conjunction with agricultural pesticides in order to boost the efficacy of the active ingredient(s). The adjuvants themselves are largely assumed to be biologically inert and are therefore subject to minimal scrutiny and toxicological testing by regulatory agencies. Honey bees are exposed to a wide array of pesticides as they conduct normal foraging operations, meaning that they are likely exposed to spray adjuvants as well. It was previously unknown whether these agrochemicals have any deleterious effects on honey bee behavior. Methodology/Principal Findings: An improved, automated version of the proboscis extension reflex (PER) assay with a high degree of trial-to-trial reproducibility was used to measure the olfactory learning ability of honey bees treated orally with sublethal doses of the most widely used spray adjuvants on almonds in the Central Valley of California. Three different adjuvant classes (nonionic surfactants, crop oil concentrates, and organosilicone surfactants) were investigated in this study. Learning was impaired after ingestion of 20 μg organosilicone surfactant, indicating harmful effects on honey bees caused by agrochemicals previously believed to be innocuous. Organosilicones were more active than the nonionic adjuvants, while the crop oil concentrates were inactive. Ingestion was required for the tested adjuvant to have an effect on learning, as exposure via antennal contact only induced no level of impairment. Conclusions/Significance: A decrease in percent conditioned response after ingestion of organosilicone surfactants has been demonstrated here for the first time. Olfactory learning is important for foraging honey bees because it allows them to exploit the most productive floral resources in an area at any given time. Impairment of this learning ability may have serious implications for foraging efficiency at the colony level, as well as potentially many social interactions. Organosilicone spray adjuvants may therefore contribute to the ongoing global decline in honey bee health.

Original languageEnglish (US)
Article numbere40848
JournalPloS one
Volume7
Issue number7
DOIs
StatePublished - Jul 16 2012

Fingerprint

Honey
Bees
Surface-Active Agents
adjuvants
Crops
Agrochemicals
honey bees
learning
Learning
Pesticides
Oils
Aptitude
Eating
Nonionic surfactants
surfactants
oil crops
Assays
ingestion
agrochemicals
foraging

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General

Cite this

Ciarlo, T. J., Mullin, C. A., Frazier, J. L., & Schmehl, D. R. (2012). Learning impairment in honey bees caused by agricultural spray adjuvants. PloS one, 7(7), [e40848]. https://doi.org/10.1371/journal.pone.0040848
Ciarlo, Timothy J. ; Mullin, Christopher A. ; Frazier, James L. ; Schmehl, Daniel R. / Learning impairment in honey bees caused by agricultural spray adjuvants. In: PloS one. 2012 ; Vol. 7, No. 7.
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Ciarlo, TJ, Mullin, CA, Frazier, JL & Schmehl, DR 2012, 'Learning impairment in honey bees caused by agricultural spray adjuvants', PloS one, vol. 7, no. 7, e40848. https://doi.org/10.1371/journal.pone.0040848

Learning impairment in honey bees caused by agricultural spray adjuvants. / Ciarlo, Timothy J.; Mullin, Christopher A.; Frazier, James L.; Schmehl, Daniel R.

In: PloS one, Vol. 7, No. 7, e40848, 16.07.2012.

Research output: Contribution to journalArticle

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