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Title: Landscape and pesticide effects on honey bees: forager survival and expression of acetylcholinesterase and brain oxidative genes

Author
item ALBURAKI, MOHAMED - University Of Tennessee
item STECKEL, SANDRA - University Of Tennessee
item CHEN, DENIZ - North Carolina State University
item MCDERMOTT, ERIN - North Carolina State University
item Adamczyk, John
item Weiss, Milagra
item SKINNER, JOHN - University Of Tennessee
item KELLY, HEATHER - University Of Tennessee
item LORENZ, GUS - University Of Arkansas
item TARPY, DAVID - North Carolina State University
item Meikle, William
item STEWART, SCOTT - University Of Tennessee

Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2017
Publication Date: 2/15/2017
Citation: Alburaki, M., Steckel, S.J., Chen, D., McDermott, E., Adamczyk Jr., J.J., Weiss, M., Skinner, J.A., Kelly, H., Lorenz, G., Tarpy, D.R., Meikle, W.G., Stewart, S.D. 2017. Landscape and pesticide effects on honey bees: forager survival and expression of acetylcholinesterase and brain oxidative genes. Apidologie. doi:10.1007/s13592-017-0497-3.

Interpretive Summary: The effects of agricultural pesticides on honey bee (Apis mellifera L.) health has been the source of much recent debate. Since honey bees have an internal mechanism to degrade or detoxify certain pesticides into less harmful forms, we tested the level of those detoxification enzymes in their brains for possible exposure to chemical pesticides in four different landscapes in West Tennessee, USA. Our data showed that pesticides were identified at lethal and sublethal doses in cotton, sorghum, and soybean flowers. Recovered honey bees contained low doses of insecticides except those foraging in non-agricultural areas. No significant differences in mortality were found between honey bees foraging in agricultural areas and non-agricultural areas. When we measured detoxification enzymes, we only found a few that varied between control bees (those that did not leave the hive) and recovered foragers (those honey bees that were foraging in the landscape).

Technical Abstract: The aim of the present work was to assess the effects of agricultural pesticides on honey bee (Apis mellifera L.) survival and physiological stress. Integrated use of acetylcholinesterase (AChE) and antioxidant enzymes (catalase and glutathione S-transferase) was tested on honey bee brains for detecting possible exposure to chemical pesticides. A large number of foragers were tracked in situ during their foraging activity in four different landscapes in West Tennessee, USA. Those landscapes included three agricultural (AG) areas that contained large field crops and one control treatment with no agriculture (non-AG). Flowering crops (corn, cotton, soybean, and sorghum) available for bees at each location were sampled and analysed for pesticide residues. After a few weeks of foraging in the surrounding agricultural areas, marked bees were recovered from their colonies and analysed chemically. In addition, four 1-day-old honey bee cohorts were fed imidacloprid in vitro ad libitum for several weeks and were used to measure gene expression of AChE and detoxification enzymes (CAT, GSTd1, GSTs3, and GSTs4) by RT-qPCR. Our data showed that pesticides were identified at lethal and sublethal doses in cotton, sorghum, and soybean flowers. Recovered foragers contained low doses of insecticides except those foraging in non-AG area. No significant differences in foragers’ mortality were found between bees foraging in AG and non-AG areas. AChE activity and other detoxification enzymes showed no response to pesticide exposure except for GSTs3 and GSTs4, which varied between control bees and recovered foragers. Our results suggest that none of the studied genes make suitable biomarkers for honey bee pesticide exposure.