Bees Know Social Distancing:

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Bees Know Social Distancing:
Increase Hive Spacing to Reduce Varroa and Viruses
Theresa J. Martin

Beekeepers are well-aware that the parasitic mite, Varroa destructor, is “… the greatest biotic threat to honey bees” (Dynes et al., 2019, p. 2). The best available science recommends practicing integrated pest management (IPM) to combat Varroa. IPM means employing multiple actions to reduce Varroa in as many ways as possible, thereby reducing parasitic and viral damage, thresholds are exceeded less frequently, and treatments are needed less often.1

One non-chemical IPM action that reduces Varroa and virus transmission is to increase colony spacing and differentiate hives.

Far Apart and Low Density
When swarming and choosing their new home, colonies space themselves far apart and with low density. At least eight peer-reviewed studies from different countries surveyed rural and natural settings to quantify distance and density of non-managed colonies. These studies show that colony density is low, with three colonies per square mile or about one colony per 250 acres. Colonies space themselves far apart as well, approximately 2,500 feet from each other. Researchers postulate colonies maintain low density and spread themselves out to optimize survival in multiple ways, such as reduced drift and horizontal pathogen transmission, reduced robbing, and reduced competition for forage.2

Drift is when a worker or drone enters a colony that is not her or his own. Drift increases the likelihood of horizontal pathogen transmission. In a superorganism such as a colony of honey bees, horizontal transmission means the pathogen from one colony is transferred to a different colony. Horizontal transmission is a survival strategy that favors pathogen virulence. Because the pathogen transfers to a new host colony, the pathogen survives even if the pathogen kills the original host colony. Through a combination of drift and robbing, Varroa easily disperses from a collapsing, dying colony to a new colony. Multiple studies show this leads to stronger Varroa, not stronger bees.3

While research varies on the median distance foragers fly to collect nectar and pollen, the accepted distance is within about a 2-mile radius from the hive. Less densely packed colonies translate into more forage available for the fewer colonies. When colonies are too densely packed, competition for limited resources increases so that there is less nectar and pollen available per colony, reducing overall foraging efficiency and ultimately, survival.

Conventional Apiary Design
Most beekeepers are taught to place hives a few feet apart on hive stands (Figure 1). Hives are often painted white with entrances facing the same direction. In addition, some beekeepers maintain a high density of colonies, with 25–100 colonies in a tightly packed apiary. Beekeepers keep colonies close together in apiaries because it is more practical and convenient for the beekeeper.

One study showed that traditional apiary settings facilitate up to 40% of workers to drift into other colonies, enabling contagious pathogens—such as European foulbrood, American foulbrood, chalkbrood, and Vairimorpha (Nosema) ceranae, Varroa, and viruses — to transfer from one colony to another.

Practice to Increase Bee Health and Productivity
Especially for the hobbyist, beekeepers can space hives farther apart, distinguish them using color, and position them with entrances facing different directions (Figure 2). A bee’s eyesight is excellent at discerning shapes and colors, so differentiating hives can reduce forager and drone drift, and queen loss. Bees orient using landmarks, such that entrances facing different directions enable returning bees to more reliably locate their colony.

One study combined these suggestions and found significant health advantages: three times lower forager drift, lower Varroa levels in brood, greater honey production, and reduced overwinter mortality (Figure 3).4 Another study compared traditional and dispersed arrangements and found significant health advantages in the dispersed arrangement: 35% lower drone drift, lower Varroa infestations, and significantly higher survival (Figure 4).5 Studies show that hives spaced just 100 feet apart on opposite corners of a suburban yard can reduce drift and Varroa loads.6

My Implementation
My first criterion when selecting a location for my bees is how far apart I can space my colonies. I keep 20–25 colonies in four locations, with no more than 11 colonies per location. In my suburban locations, I place colonies 100 feet apart on opposite corners of the homeowner’s yard (Figure 5). In addition, hives are painted different colors to help the bees distinguish between them.

I observed the benefits of increased colony spacing and low density while participating in the USDA APHIS National Honey Bee Survey. The Kentucky state apiarist, Dr. Tammy Horn Potter, took samples from my colonies for pathogen analysis. One of my colonies had been struggling with chronic bee paralysis virus (CBPV) (Figure 6). Dr. Potter commented that the distance between my colonies was likely a factor in limiting CBPV to only one colony, as no other colony showed clinical signs.

100 Feet Apart Matters
Dr. Thomas Seeley (2019) writes in The Lives of Bees that “… spacing colonies just 30-50 meters (100-160 feet) apart greatly reduces the likelihood of drifting of drones — and probably also workers — among colonies and thus the spreading of diseases” (p. 287). Increased space between hives reduces the damage caused by Varroa, viruses and other contagious pathogens, and improves the health and productivity of our bees.

Theresa J. Martin is the author of Dead Bees Don’t Make Honey: 10 Tips for Healthy Productive Bees, which includes a Foreword written by Dr. Thomas Seeley. Theresa has achieved 99% colony survival and honey production that is above the local average in her six years as a beekeeper, with 20–25 colonies in Kentucky. She is a Cornell Master Beekeeper, 2024 Kentucky State Beekeeper of the Year, and Vice President of the Kentucky State Beekeepers Association. Theresa can be reached at theresa@littlewolf.farm

References:
1The Honey Bee Health Coalition provides outstanding Varroa and integrated pest management resources. Honey Bee Health Coalition. (2022). The guide to effective Varroa sampling and control. https://honeybeehealthcoalition.org/wp-content/uploads/2022/08/HBHC-Guide_Varroa-Mgmt_8thEd-082422.pdf
2Seeley (2019) provides a table on page 41 summarizing eight studies conducted worldwide that demonstrate low colony density when colonies are choosing their own home. Seeley, T. D. (2019). The Lives of Bees: The Untold Story of the Honey Bee in the Wild. Princeton University Press.
3Multiple research papers describe horizontal pathogen transmission for honey bees, Varroa, and the viruses Varroa vector.
Dynes, T. L., Berry, J. A., Delaplane,
K. S. de Roode, J. C., Brosi, B. J.
(2020). Assessing virulence of Varroa
destructor mites from different honey
bee management regimes. Apidologie,
51, 276–289. https://doi. org/10.1007/s13592-019-00716-6
Forfert, N., Natsopoulou, M. E.,
Frey, E., Rosenkranz, P., Paxton,
R. J., Moritz, R. F. (2015). Parasites
and pathogens of the honeybee
(Apis mellifera) and their influence
on inter-colonial transmission.
PLOS ONE. https://doi.org/10.1371/journal.
pone.0140337
Ingemar, F., Scott, C. (2001).
Implications of horizontal and
vertical pathogen transmission for
honey bee epidemiology.
Apidologie, 32(3), 199-214. https://doi.org/10.1051/apido:2001122

4Dynes, T. L., Berry J. A., Delaplane K. S., Brosi, B. J., de Roode, J. C. (2019). Reduced density and visually complex apiaries reduce parasite load and promote honey production and overwintering survival in honey bees. PLOS ONE, 14(5): e0216286. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0216286

5Seeley, T. D., Smith, M. L. (2015). Crowding honeybee colonies in apiaries can increase their vulnerability to the deadly ectoparasite Varroa destructor. Apidologie, 46, 716–727. https://doi.org/10.1007/s13592-015-0361-2

6On pages 259-263, Seeley (2019) summarizes the science related to natural colony spacing advantages, horizontal transmission, and his 2015 research. On page 287, he applies this research, offering suggestions for increased colony spacing.