Benefits of Propolis to Honey Bee Health and Immunity

Project Overview

Project Type: Graduate Student
Funds awarded in 2012: $9,900.00
Projected End Date: 12/31/2015
Grant Recipient: University of Minnesota
Region: North Central
State: Minnesota
Graduate Student:
Faculty Advisor:
Marla Spivak
University of Minnesota

Annual Reports


  • Animals: bees


  • Animal Production: general animal production

    Proposal abstract:

    Honey bees are the world’s most important pollinator of crops. However, honey bees are in crisis due to interacting effects of pathogens, parasites and poor nutrition, which impairs their immune system and leads to the colony death. Honey bees, as social insects, rely on collective behavioral defense mechanisms called social immunity to augment the immune system of individual bees. One of these behavior defenses is the collection and deposition of antimicrobial plant resins in the nest as a form of cement, called propolis by beekeepers. We documented that propolis reduces the amount of microbes in the nest and reduces individual bee investment in immune responses. Feral honey bee colonies nesting in trees construct a heavy propolis envelope inside the nest cavity, but colonies in commercial beekeeping equipment are not able to attach a propolis envelope on the smooth surface of the pine boxes. The short-term objectives of this proposal are 1) to test “propolis trap” configurations to encourage bees to deposit propolis naturally in beekeeping equipment and quantify the relative benefit to the immune system of 7d old bees using real-time PCR of immune gene transcripts; and 2) to determine if a propolis envelope can reduce the growth of molds within the nest cavity in early spring and thus improve colony health during this vulnerable stage in colony life-history. The intermediate-term outcome is to modify standard beekeeping equipment to encourage bees to deposit an antimicrobial propolis envelope in a way that most benefits their immune systems. In the long term, this research will promote the health and immune system function of important honey bee pollinators in the North Central region and nationwide.

    Project objectives from proposal:

    Objective 1: Test “propolis trap” configurations to quantify their relative benefit to the immune system of individual bees and thus the social immunity of the colony. Thirty-six colonies will be established in new 10-frame equipment in mid-April. Sister queens will be introduced into each colony to reduce genetic variation. Twelve colonies will be provided with nylon ¼” mesh cloth stapled to the four inner walls of each bee box and to the top of the wooden frames(containing wax combs) to encourage the bees to build a propolis envelope. This nylon mesh is used by Canadian researcher (Dr. T. Szabo) and we have confirmed its efficacy in preliminary trials. Another 12 colonies will be provided with the mesh propolis traps only on top of the frames, as is done to collect propolis commercially. The last 12 colonies will serve as controls; no mesh will be provided and the bees will deposit propolis in the cracks and crevices within the box where they can. When the colonies have filled in the mesh with propolis (2-3 months after colony establishment) I will mark newly emerging bees and collect at least 50 bees per colony after 7 days exposure within the propolis-treated colonies to analyze their immune-gene expression between treatments and to determine levels of bacterial load, following methods used by Simone et al (2009). Total RNA will be isolated from individual bees using RNAqueous-96 Kit (Ambion, Austin, TX). RNA will be pooled by colony prior to cDNA synthesis and quantified using real-time PCR. I am currently analyzing immune gene transcripts for another thesis study, and so am proficient in these methods. I will assess colony strength (frames of bees and brood; Nasr et al. 1990), levels of diseases (Varroa, Nosema, American foulbrood, chalkbrood, and viruses, following methods routinely used in the Spivak lab (Spivak and Reuter, 2001; Lee et al., 2010; Chen et al., 2005; D. Tarpy can assist with viral analysis if needed). Transcripts of immune-related genes (following Simone et al., 2009) and assessments of colony heath will be compared among treatments, and the amount of propolis collected (by weighing the traps) will be determined to quantify if there is a correspondence between the amount of propolis in the envelope and colony’s health. This experiment will be repeated over two summers if necessary.
    Objective 2: Determine if a propolis envelope can reduce the growth of molds within the nest cavity in early spring, and thus improve colony health. Another set of 20 colonies will be established in new equipment in April and will be allowed to develop into large colonies with large honey stores for winter. Ten colonies will be encouraged to build a propolis envelope using the mesh stapled to the inside of all boxes, and another 10 will not be provided mesh as controls. Assessments of colony strength, disease and mite levels will be made as in Objective 1 before winter. I will winter the colonies with the propolis traps inside, to determine if the propolis envelope benefits bees during early spring by eliminating molds that develop in the boxes at that time. The success of the propolis envelope will be assessed by quantifying quantity of mold within the nest using a ranking system, and collecting the same measures of colony strength and health. These measurements will be taken on April of the following year. The experiment will be repeated the following year, if needed.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.