For the Love of Bees and Beekeeping
On Comb Replacement
by Keith Delaplane
One of the brightest spots on the American beekeeping landscape is the Bee Informed Partnership http://beeinformed.org. BIP is a USDA-funded consortium of university and USDA bee scientists focused on surveying the beekeeping industry to identify management factors that affect colony health and survival. The nice thing about BIP surveys is that the data are summarized and the trends publicized on the BIP website. One need only peruse the BIP homepage to get an appreciation of the power of data and its ability to strip away guesswork and make sense of complicated phenomena. There one finds not only annual colony loss reports, but clear and succinct summaries of noteworthy trends in the surveys that give clues to good management.
It is one of these succinct summaries that caught my attention the other day. The online BIP article, “Brood comb management and treatment of dead outs: National management survey 2011-2012” informs us that beekeepers who replaced 50% or more of the brood combs in their colonies experienced 30.7% colony overwinter loss; beekeepers who replaced 10% of brood combs lost 21%, and beekeepers who replaced none of their combs lost 22%. The 30.7% loss rate suffered by the 50% replacers was statistically significant.
I admit these results surprised me, as I count myself among the many voices down the years who have advocated that beekeepers should regularly replace their brood combs. My opinions on this matter draw mainly from the research of my first graduate student, subsequent lab manager, and now authority in her own right, Jennifer Berry. One of the chapters of Jennifer’s master’s thesis dealt with the effects of old brood combs on colony strength.1 In each of three years she set up apiaries of 21-24 four-frame Langstroth nucleus colonies and assigned each colony one of two treatments – establishment on first-year, newly-drawn beeswax brood combs or establishment on old black combs of unknown age (Fig. 1). She then tracked colony brood production, brood survivorship, emergent adult weight, and adult populations. We measured brood production by overlaying a plexiglass grid marked in square centimeters over the brood and visually adding it up (Fig. 2). We measured brood survivorship by overlaying a sheet of transparent acetate onto a comb and marking on it the location of 10-40 cells of live, uncapped larvae (Fig. 3). Three days later we returned the sheet of acetate to its corresponding frame and made note of surviving brood to determine percentage survivorship.
Colonies housed on new comb produced more brood and heavier ...