Final Report for FNE05-560
As many readers know all to well, the practice of wrapping bee hives for the winter was once widespread throughout the Northeastern United States. However, in the mid 1970's something changed here in Western Massachusetts and this practice has become relatively uncommon for both the hobbyist and sideliner (< 100 colonies). Although the reasons behind the abandonment of this practice by Massachusetts beekeepers are not well understood, the persistent threat of pathogenic colony combined with escalating package/nuc costs (~$65 & $90 respectively) have once again made over-wintering success critical for sustainable beekeeping.
It doesn't require much cognitive effort to imagine that wrapping beehives with insulation in the late fall should result in both fewer dead-outs (colony loss from starvation or pathogenic attack) and larger surviving worker bee populations. Herein lies a dilemma: is our urge to promote "winter comfort" to hives merely an anthropomorphic expression of our own winter bundling? For instance, thanks to its latitude and maritime influences, Massachusetts typically experiences moderate winters, averaging 120 frost-free growing days per year. Perhaps our forbearers had fallen victim to the Yankee adage that a well insulated house is a good house when in actuality, Massachusetts' winters do not merit seasonal wrapping. If the truth is not clear (as is usually the case, a convenient continuing employment act for those of us comfortably ensconced in academia) could wrapping actually prove detrimental under mild winter conditions?
With this notion in mind I felt emboldened to test the theory that perhaps we have become complacent, remiss in our apicultural stewardship duties to provide an ideal nest habitat. Should this trial prove true, we, by failing in our insulation responsibilities have only to look in the mirror to ascribe blame for declining wintering success. I realize that I am far from a watershed moment here, as similar tests have been performed before. With this in mind, and to avoid simply testing the usefulness of a once common practice, this investigation involved the comparison of traditional wrappings with one of the latest wintering products available to the beekeeping industry. This trial was made possible with funding from the USDA sustainable agriculture research and education (SARE) program.
This randomized complete block design study was comprised often experimental units, each with three hives. Hives were selected for measurement from four apiaries local to Amherst, Massachusetts (42.380N, 72.523W) with double deep configuration (two deep supers) and similar colony strength. Involved colonies had not received any chemical treatments, prophylactic or otherwise, within six months of trial initiation.
It must be noted that some of the involved hives included slatted racks: however, the possible effects of such equipment were not considered by this experiment. As is becoming the norm in this area, all involved colonies stemmed from Russian hybrid queens, most of which were open-mated with local drone stock. Finally, to promote ventilation and winter cleansing flights during heavy snow cover, all hives were afforded upper entrances by notching their inner covers.
Colonies within each experimental unit were randomly assigned a treatment: traditional wrapping (tar paper), heavy wrapping (blackened corrugated cardboard with closed foam insulation), or control (unwrapped). Traditional wrapping involved stapling a precut (~20" x 76") piece of 15-weight black roofing felt around the hive bodies. Ample stapling was exercised in an attempt to provide a layer of trapped air around the hive. Heavy wrapping was more involved; colonies were surrounded with "loose fit", waxed and corrugated, black cardboard shells enclosing 1" thick sheets of precut (by the beekeeper) 15 psi closed-cell styrofoam boards (R-value 5 at 75°F). Upper entrances were cut through both insulation materials. Control hives were left unwrapped. Treatment costs and efforts are presented in figure 1.
Wrapping Type....Cost per colony....Instillation time per colony
* Materials are reusable
To evaluate treatment effects on honey store consumption, hives were weighed prior to wrapping in the early winter (December) and again in the early spring (March) when wrappings were removed. Data constituted winter store consumption when spring weights were subtracted from pre-treatment weights. The treatment period, although arguably short (10 weeks), was intentionally constrained to non-flying weather in order to minimize the effects of inter-colony robbing. Hive weighing was performed by inserting a platform (resembling a child's swing seat) below each hive. Suspending ropes (one at each corner) for the platform came together below a self-dampened digital suspension scale. Hives were lifted via a bar suspended between the shoulders of two technicians (metal suspension bar was later replaced by two deceased hockey sticks, much to the relief of all involved). To enable greater statistical latitude, hive weights were recorded to the nearest 1/10 of a pound.
As a result of treatment, it was determined that heavy wrapping did not significantly improve the consumption efficiency of winter stores. However, colonies that were wrapped in tar paper lost significantly less weight than untreated hives. Pre-treatment hive varied from 80-126.5 lb (a typical spread for the region) while individual winter store consumption over the 10-week treatment period varied from 2.3-19.9 lb. All three treatments experienced a 20% mortality rate.
Despite the mild New England winter of 2005-06. heavily wrapped hives displayed a similar pattern of honey consumption with control hives. It is speculated that heavy insulation allowed for more cluster activity and lower worker mortality throughout the winter season. This improved survivorship and increased activity appears to have resulted in a greater demand for stored honey. Another possible explanation for the extent of store consumption within the heavily wrapped hives is that the added insulation afforded these colonies a warmer nest, allowing for an earlier quickening of spring buildup. Such activity costs a colony weight. Although the product of store consumption (honey and pollen) will remain as a new worker there will be both energy and humidity released through metabolism.
If this theory is true, heavily wrapped hives, by starting to build up before the other two treatments, may have actually been ahead of the game. Because of continued cool temperatures at the time of press, I have not been able to verify my suspicions and evaluate the effect of treatment on brood nest size. Anecdotally. the largest apparent population exists within a hive that was heavily wrapped. Additional testing is necessary to verify this theory and to determine if wrapping strategy is correlated with internal hive temperature.
Overall, this experiment has suggested that despite a lack of severe winter weather, the effort required for wrapping hives was well spent as it appears that colonies benefited from the endeavor. However, such gains need to be weighed against the requirements from beekeepers. With this is mind, it is clear that the cost to benefit relationship presented by wrapping with tar paper is the best strategy for Western Massachusetts.
Special thanks to: Kate Parrott, Dan Conlon, Warm Colors Apiary, Black Dog Apiary and the Laurin family. Without their generous help this project could not have been possible.
Please feel free to contact me with questions at (413) 367-7592 or firstname.lastname@example.org