3: Pesticides and propolis: The influence of honey bee-collected plant resins on pesticide exposure and sensitivity in agroecosystems

Managed honey bee (Apis mellifera) colonies are currently experiencing high rates of annual mortality, largely due to pathogens, parasites, pesticides and poor nutrition. Pesticides have many detrimental effects on honey bee colony health and survival and mediating their impacts is a major concern for beekeepers. Honey bees collect antimicrobial plant resins and incorporate them as part of the internal nest structure as propolis. Propolis can reduce colony microbial loads, enhance bee immune function, as well as increase expression of detoxification enzymes, enhance metabolism, and protect against insecticide induced mortality. Our hypothesis is that the presence of propolis in the hive primes the detoxification pathways so that the honey bee more quickly and effectively detoxifies pesticides. 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, pesticide exposure and sensitivity in a commercial beekeeping operation and in stationary hives. 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 and metabolic detoxification in honey bees raised in enhanced propolis deposition environments will be discussed. The anticipated outcomes of this project is to make recommendations on colony management practices that may mediate the impacts of pesticides and ultimately further elucidate the intricate role of propolis on individual bee and colony health.