Impact of propolis on colony heath and pesticide exposure in agroecosystems

Honey bees collect antimicrobial plant resins and incorporate into the internal nest structure as propolis. Propolis can reduce colony microbial loads and modulate immune function, and in laboratory experiments can increase expression of detoxification enzymes and protect against insecticide-induced mortality. The intricate role of propolis on individual bee and colony health is further compounded by other environmental conditions including resource availability and pesticide exposure. Thus, a “real-world” test of the effect of a propolis-enriched hive environment on colonies involved in commercial, migratory beekeeping has been much needed. In this project, we used hive bodies with rough sided interiors that promote propolis deposition as part of a large-scale effort to examine the role of propolis with respect to bee health and pesticide exposure in a commercial beekeeping operation. Results of colony health metrics in relation to this propolis-enhanced environment will be presented along with the first report of pesticide residues in propolis. Additional experiments assessing insecticide sensitivity in honey bees raised in enhanced propolis deposition environments will be discussed. Overall, findings indicate that propolis harbors a significant number of pesticides, but potential costs of that appear to be minimal as propolis-enriched colonies have larger populations at the end of the season.