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J Vis Exp. 2017 Oct 9;(128). doi: 10.3791/54631.

Empirical, Metagenomic, and Computational Techniques Illuminate the Mechanisms by which Fungicides Compromise Bee Health.

Author information

Vegetable Crop Research Unit, USDA-ARS; Department of Entomology, University of Wisconsin-Madison;
Department of Entomology, University of Wisconsin-Madison.
Department of Horticulture, University of Wisconsin-Madison; Instituto Nacional de Investigaciones Forestales, Agricolas y Pecuarias.
Department of Bacteriology, University of Wisconsin-Madison.
Vegetable Crop Research Unit, USDA-ARS; Department of Horticulture, University of Wisconsin-Madison.
Laboratory of Genetics, Genome Center of Wisconsin; DOE Great Lakes Bioenergy Research Center, Wisconsin Energy Institute; J.F. Crow Institute for the Study of Evolution, University of Wisconsin-Madison.


Growers often use fungicide sprays during bloom to protect crops against disease, which exposes bees to fungicide residues. Although considered "bee-safe," there is mounting evidence that fungicide residues in pollen are associated with bee declines (for both honey and bumble bee species). While the mechanisms remain relatively unknown, researchers have speculated that bee-microbe symbioses are involved. Microbes play a pivotal role in the preservation and/or processing of pollen, which serves as nutrition for larval bees. By altering the microbial community, it is likely that fungicides disrupt these microbe-mediated services, and thereby compromise bee health. This manuscript describes the protocols used to investigate the indirect mechanism(s) by which fungicides may be causing colony decline. Cage experiments exposing bees to fungicide-treated flowers have already provided the first evidence that fungicides cause profound colony losses in a native bumble bee (Bombus impatiens). Using field-relevant doses of fungicides, a series of experiments have been developed to provide a finer description of microbial community dynamics of fungicide-exposed pollen. Shifts in the structural composition of fungal and bacterial assemblages within the pollen microbiome are investigated by next-generation sequencing and metagenomic analysis. Experiments developed herein have been designed to provide a mechanistic understanding of how fungicides affect the microbiome of pollen-provisions. Ultimately, these findings should shed light on the indirect pathway through which fungicides may be causing colony declines.

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