Evolutionary ecology could benefit beekeepers battling diseases

Some commercial beekeeping practices may harm honey bees more than help them

Date: August 28, 2017

Source: Materials provided by Emory Health Sciences. Originally written by Carol Clark. Note: Content may be edited for style and length.

Summary: A review paper draws on scientific studies to recommend ways to reduce honey bee disease impacts, such as limiting the mixing of bees between colonies and supporting natural bee behaviors that provide disease resistance.

An electron micrograph shows a Verroa destructor mite (right) on an adult honey bee host. The parasitic Varroa mite and the numerous viruses it carries are considered the primary causes of honey bee colony losses worldwide. (USDA photo)

Some commercial beekeeping practices may harm honey bees more than help them, scientists warn in a paper published in the journal Nature Ecology and Evolution.

“Western honey bees — the most important pollinators for U.S. food crops — are facing unprecedented declines, and diseases are a key driver,” says Berry Brosi, an evolutionary biologist at Emory University and a lead author of the review paper. “The way commercial operations are managing honey bees might actually generate more damaging parasites and pathogens by creating selection pressure for higher virulence.”

The paper draws on scientific studies to recommend ways to reduce disease impacts, such as limiting the mixing of bees between colonies and supporting natural bee behaviors that provide disease resistance. The paper also highlights honey bee management practices in need of more research.

During the past 15 years, ecological and evolutionary approaches have changed how scientists tackle problems of infectious diseases among humans, wildlife and livestock. “This change in thinking hasn’t sunk in with the beekeeping field yet,” says Emory evolutionary biologist Jaap de Roode, co-lead author of the paper. “We wanted to outline scientific approaches to help understand some of the current problems facing beekeepers, along with potential control measures.”

Co-authors of the paper include Keith Delaplane, an entomologist at the University of Georgia, and Michael Boots, an evolutionary biologist at the University of California, Berkeley.

Managed honey bees are important to the production of 39 of the 57 leading crops used for human consumption, including fruits, nuts, seeds, and vegetables. In recent years, however, managed honey bee colonies have declined at the rate of more than one million per year, representing annual losses between 30 and 40 percent.

Two drone pupae of the Western honey bee infected with Varroa mites. (Photo by Waugsberg via Wikipedia Commons.)

While pesticides and land-use changes are factors involved in these losses, parasites are a primary driver — especially the aptly named Varroa destructor. The parasitic Varroa mite and the numerous viruses it carries are considered the primary causes of honey bee colony losses worldwide.

Varroa mites are native to Asia, where the Eastern honey bee species co-evolved with them before humans began managing bee colonies on commercial scales. As a result of this co-evolution, the Eastern honey bee developed behaviors — such as intensive mutual grooming — that reduce the mites’ negative impacts.

The Western honey bee species of the United States and Europe, however, has remained relatively defenseless against the mites, which spread to the United States during the late 1970s and 1980s. The mites suck the blood of the bees and reduce their immunity. Even more potentially destructive, however, are the multiple viruses the mites transmit through their saliva. Deformed-wing virus, for instance, can cripple a honey bee’s flying ability and is associated with high bee larval mortality.

Following are some of the potential solutions, in need of further study, outlined in the Nature Ecology & Evolution paper.

Reduce mixing of colonies: A common practice at beekeeping apiaries is to move combs containing brood — eggs and developing worker bees — between colonies. While the practice is meant to equalize colony strength, it can also spread parasites and pathogens.

Colonies are also mixed at regional and national scales. For instance, more than half of all honey bees in the country are involved in almond pollination in California. “For a lot of beekeeping operations, trucking their bees to California for almond pollination is how they make ends meet,” Brosi says. “It’s like the Christmas season for retailers.”

Pollination brokers set up contracts for individual beekeepers on particular almond farms. “If the brokers separated individual beekeeping operations beyond the distance that the average honey bee forages, that could potentially help reduce the mixing of bees and the rate of pathogen transmission between the operations,” Brosi says.

Varroa destructor (USDA)

Improve parasite clearance: Most means of dealing with Varroa mites focus on reducing their numbers in a colony rather than wiping them out, as the mites are developing increased resistance to some of the chemicals used to kill them. Such incomplete treatments increase natural selection for stronger, more virulent parasites. Further compounding the problem is that large commercial beekeeping operations may have tens of thousands of colonies, kept in close quarters.

“In a natural setting of an isolated bee colony living in a tree, a parasite that kills off the colony has nowhere to go,” de Roode explains. “But in an apiary with many other colonies nearby, the cost of parasite virulence goes way down.”

Allow sickened colonies to die out: Keeping bees infected with parasites and viruses alive through multiple interventions dilutes natural selection for disease resistance among the bees. In contrast, letting infections take their course in a colony and using the surviving bees for stock could lead to more resistant bees with fewer disease problems.

Support behavioral resistance: Beekeepers tend to select for bees that are more convenient to manage, but may have behavioral deficiencies that make them less fit. Some honey bees mix their saliva and beeswax with tree resin to form what is known as propolis, or bee glue, to seal holes and cracks in their hives. Studies have also shown that propolis helps keep diseases and parasites from entering the hive and inhibits the growth of fungi, bacteria, and mites.

“Propolis is sticky. That annoys beekeepers trying to open hives and separate the components so they try to breed out this behavior,” de Roode says.

The paper concedes that commercial beekeeping operations face major challenges to shift to health management practices rooted in fundamental principles of evolution and ecology.

“Beekeeping is a tough way to make a living, because it operates on really thin margins,” Brosi says. “Even if there are no simple solutions, it’s important to make beekeepers aware of how their practices may affect bees in the long term. And we want researchers to contribute scientific understanding that translates into profitable and sustainable practices for beekeeping.”

Journal Reference:

  1. Berry J. Brosi, Keith S. Delaplane, Michael Boots, Jacobus C. de Roode. Ecological and evolutionary approaches to managing honeybee diseaseNature Ecology & Evolution, 2017; 1 (9): 1250 DOI: 10.1038/s41559-017-0246-z

September 2017 Presentation

Rebekah Golden gave us a very informative presentation on foundationless beekeeping. Most common to top-bar or Warré hives, you can even go foundationless in Langstroth hives.

Here are some helpful tips for reattaching broken or crazy comb in a Langstroth hive. Photos courtesy Susan Rudnicki.

1. Broken or cross comb removed from frame.
2. Frame placed upside-down in holding fixture.
3. Comb placed upside-down in frame against “top” bar, and inside rubber bands.
4. Zip-ties used to secure comb in place to keep it pinned against top bar.
5. More zip-ties.
6. Trim tails off zip-ties.
7. All done and ready to be returned to the hive.



2017 North American Mite-A-Thon


Mite-A-Thon is a national effort to collect mite infestation data and to visualize varroa infestations in honey bee colonies across North America within a one week window.  All beekeepers will be asked to participate, creating a rich distribution of sampling sites in Canada, the United States, and Mexico.  Their varroa monitoring data will be uploaded to www.mitecheck.com.

More information is available here.

August 2017 Presentation

Andony Melathopoulos joined us again for our August meeting and gave us a great presentation on Living with Varroa.

andony_1000x1000Andony is an Assistant Professor of Pollinator Health Extension in the Department of Horticulture at Oregon State University. His work at OSU comes out of a mandate from the Oregon Legislature to create a state-wide pollinator safety and outreach program. Prior to coming to OSU he was a Postdoctoral Scholar in the Department of Biology at the University of Calgary working with Shelley Hoover and Ralph Cartar on canola pollination. He holds an Interdisciplinary PhD from Dalhousie University (2015) and a Master of Pest Management from Simon Fraser University (1999). Formerly he worked as the chief technician in Agriculture and Agri-Food Canada’s Apiculture Research program (2000-2012).

Rebekah Golden Bio

Introducing our newest blog contributor…

Rebekah Golden discovered herself as an unexpected bee-lover working as an undergraduate research assistant in a bumblebee pollination behavior lab at the University of Arizona. She found that through bees, she was more in touch with the environment and world around her, and it wasn’t long before she became completely mesmerized by the simplicity of the individual and how that translated into the complexity of the honeybee superorganism. Using charismatic honeybees as a gateway to the ecosystem concept, Rebekah and 2 friends started Bee & Bloom LLC in Portland OR. Together they run an educational apiary with 16 hives & an online resource shining a light on pollinators, sustainability, and natural wellness.

Summer Management

The Reason Behind Honey

It’s no secret that honey bees are wholly unique from our 4,000 North American bee species. The main difference is the size, scope, and intricacy of their social system. The superorganism life history strategy bestows certain benefits to Apis mellifera, who use their vast colony numbers and communication systems to maximize collection and use of the pollen and nectar resources of their environment. Just as blooms have seasonal cycles, so do honey bees, and these 2 cycles are indelibly linked as shown in the diagrams from Ruhl Bee Supply below.  

While solitary and small social-colony bee species have some form or caste that hibernates through the winter, honey bee colonies actively survive through the cold months by clustering inside the hive and generating heat by vibrating their flight muscles. This is fueled by the spoil-proof and sugar-rich substance we know as honey. To ensure survival and reproduction of the colony as a whole, the spring months are spent building up their populations enough to swarm, and summer months are spent preparing for winter. At each stage in the warm season they must adjust their behaviors to maximize their workload to either collect as much pollen as they can to build their population, or to collect as much nectar as they can to turn into honey.

Where we fit in

As the responsible honey bee stewards we are, every time we open our hives, it is important to consider exactly what the colony should be doing at that point in the season. Summer is stressful for the bees. This is when nectar is scarce, they must defend their hive from robbing bees and yellow jackets, Varroa populations spike, and they must keep their hive cool. Additionally, colony populations are at their densest, and hive inspections can disrupt their primary goals in favor of cleaning up the mess the beekeeper left behind. It is important to go into each inspection with a goal in mind; once you’ve satisfied your goal, close up the hive and move on.

Summer and the nectar dearth

Unfortunately, the nectar dearth is here. We were hoping that this year we’d see blackberry in bloom through July, however it is becoming apparent that will not be the case. It is now that we can begin to predict whether a hive will survive the season or the winter with a higher degree of accuracy. Weak hives can be diagnosed by having low honey stores, signs of robbing,  and high mite populations. Depending on your personal management philosophy, each of these hallmarks can be responded to in order to increase their chances of survival.  


Low honey stores can be responded to by feeding. It is important to remember Boardman entrance feeders can draw robbing bees from other colonies or yellowjackets to the hive. So, break out an internal-hive feeder of your choice if your bees need a hand building up their honey stores. Additionally, move from your 1:1 sugar:water syrup ratio to 2:1. This will help them dehydrate their stores more quickly and with less effort, and will prevent too much moisture in the hive during the winter.

Robbing Prevention

Robbing can be diagnosed a few ways. The first warning sign would be remnants of warfare- large numbers of dead bees at the entrance of your hive. If you’re lucky, you may see robbing bees before this point with large numbers of bees landing on, buzzing around, and sniffing out cracks and other areas of the hive body. Foreign bees are not familiar with your hive’s entrance, but it is only a matter of time before they find it. Robbing must be responded to immediately! As soon as there are any signs, equip your hives with entrance reducers or robber screens to give your guard bees a much needed edge. These tools are also useful for preventing yellowjacket predation, which is also picking up at this time–if you haven’t broken out your yellow jacket traps yet, do it now!

Monitoring Varroa

Now, onto the lengthy topic, and bane of the modern beekeeper’s existence…Varroa mites. Regardless of your treatment philosophy, mites must be monitored and dealt with in an urban setting, where there are many managed hives in a small area. July is when we begin our more diligent mite sampling efforts. There are many ways to sample your hive for mites, though the ones I use most frequently are the sticky board method with screened bottom boards, ether rolls, or alcohol washes (if you don’t have a mite sampling kit, or don’t want to make your own, pick one up at the next PUB meeting).

Jar methods of sampling like ether rolls and alcohol washes tend to be more accurate than sticky boards. To perform these methods, collect nurse bees from the heart of your brood nest (with extra care not to collect the queen!), in a quart jar. I recommend a 300 bee sample, which is about ¾” in the bottom of the quart jar. For an ether roll, use a solid lid and spray automotive starter fluid (ether) for about 2 seconds. Then swish your bees around the inner walls of the jar, and the mites will stick. From there you can count the mites, and you can determine the ratio of infection. For an alcohol wash, drown your bees in isopropyl alcohol, and equip your jar with a mesh lid. Strain the liquid out of the jar over a coffee filter, and count the mites left behind to determine your ratio.

It is generally agreed upon that a colony with 3,000 mites cannot survive (Source). If you find 9 or more mites from your 300 bee sample, it is time to react. If you subscribe to use of chemical treatments, this would be the time to use them. If you do not use chemical treatments, my go-to response is to induce a 3-5 day brood break by caging the queen. Other options would be to re-queen if you suspect the issue is weak genetics (take context into account here- is it the genetics or external environmental factors causing the mite-spike?), add a frame of capped brood from another hive to spike the colony population, decrease hive cavity space (Source), or sift powdered sugar onto your bees to encourage them to groom (only do this if you have a screened bottom board). If the mites persist, this is the time you would choose to experiment with a treatment of your choice, or to do the hard task of killing your colony with soapy water before they spread the mites and diseases they vector to other local colonies.

Even strong colonies can be affected by high mite populations at this time; strong bees pick Varroa mites up from the weak bees during robbing, and bring them back to their hives (Source). It is of utmost importance at this point in the season to monitor and respond to mites regardless of your personal treatment philosophy. Keep in mind, it is often the viruses that mites transmit rather than the mites themselves that are directly responsible for a colony’s demise (Source). During inspections, keep your eyes open for Deformed Wing Virus, K-wing virus, and Sac Brood.

It’s not you, it’s them

It should be noted that even the most diligent and responsible beekeepers can end up with dead colonies. My best advice would be to pay attention to your bees. Allow them to take care of the problems they can handle, and when they can’t, take mindful action. Each beekeeper must craft their own management philosophy, which often entails combining elements of many separate doctrines. So long as you are responding from a place of knowledge, experience, and good intentions, you’ll be doing a service to yourself, your bees, and the greater good.

PUB June 2017 Beeline

This month we will be recapping our June 7th PUB meeting. Our next meeting is Wednesday, July 5th at Rose City Park Methodist Church from 7-9pm. Hope to see you there!

PUB President Bill Catherall started things off reminding those not on the Swarm List to register as this is the month for swarms. If you haven’t registered jump on over to the Bee Allies site and take advantage of swarm reports, mentoring opportunities, and available apiary spaces.

Glen Andresen shared his monthly Pollen & Nectar report. Glen took us through annuals, perennials, shrubs, vines and flowering trees that are contributing to this year’s honey flow. For a more detailed report check out bridgetownbees.com for Glen’s monthly “What’s in bloom” report. And please email Glen with any photos and/or suggestions of other good honey bee plants.

Our featured speaker was Brian Lacy, owner of Urban Bees And Gardens, which offers a range of programs for all ages to educate, support and advocate for the beekeeping community. Brian’s highly informative presentation covered first-year beekeeping and offered knowledge from his 45 years of beekeeping experience.

Tour De Hives 2017

Tour De Hives is just a few weeks away!! TDH is a self-guided tour of backyard apiaries and bee trees in and around Portland, Oregon. This year the tour falls on the weekend of June 24-25. We’re still looking for volunteers so please sign up here. Saturday we will be exploring SE neighborhoods and Sunday will be in NE Portland neighborhoods. We hope this will help give people more time to enjoy the tour stops, create more traffic at more stops, and give tour hosts a chance to also take the tour. Get your tickets here!

Zenger Work Party June 18th

Also a reminder/invite for the work party at Zenger Farm on June 18th from 10am-noon. We’ve been doing great things at Zenger and the apiary is looking awesome. But there’s still more to be done.

PUB Member Survey

At Portland Urban Beekeepers, we are honored to host a place for beekeepers to come together to learn, share, and engage our greatest passion – bees! Beekeeping is an exciting and challenging journey, and we all have our own unique experiences. We want to take this opportunity to learn more about who makes up our beekeeping club! Please click this link to fill out the online survey. We thank you for being a part of our community!

Multnomah County Fair

PUB’s presence at the 111th Multnomah County Fair was it’s best ever. The observation hive was a huge hit (thanks Bill Catherall & Janene Gibbs), as was the face cutout photo board. Special thanks to Linda Zahl for organizing and staffing the event and to all the volunteers who donated their time to making it a huge success!! Part of PUB’s commitment is to advocate for the bee community and educate those interested in raising honey bees and supporting their presence in the environment and we hit our mark at this year’s fair. Well done everyone!!

May 2017 Beeline

In this month’s Beeline we will be recapping our May 3rd PUB meeting. We met at our usual location at Rose City Park United Methodist Church – and will be again on Wednesday, June 7th from 7-9pm. Dewey Caron shared information on swarms in May. He also shared an important link about the impact of pesticides on our bees. Go to http://pesticideimpacts.org for more information.


Glen Andresen shared his monthly Pollen & Nectar report. We’re seeing annual flowers such as the Hybrid Poppy, and bulbs like the crocus bellflower (campanula), as well as the usual suspects like the sweet cherry and the asian pear starting to bud and flower. For a more detailed report check out bridgetownbees.com for Glen’s monthly “What’s in bloom” report. Send photos and suggestions of other good honey bee plants to glen@bridgetownbees.com.

baithivesSwarm Traps! By setting out swarm traps we can make it easier to catch our own swarms and give swarming bees a place to move into instead of a neighbor’s wall or attic space. And there’s no better time to catch swarms than right now! For information on how to catch swarms and to download swarm trap plans check out PUB’s blog post here. If you don’t want to build your own bait hives, we still have a few still available for purchase for $30 ($25 for 2 or more) so contact Lauren Smith  to order.

Our May meeting featured Rebekah Golden, who gave a wonderful presentation about her experiences working with native bees. Rebekah loves talking about all types of pollinators and is the education coordinator over at Bee Thinking. She was nice enough to allow us to post it on our blog so head over and check it out. We are so grateful to Rebekah for taking the time to share with our group.

Come check us out at the Multnomah County Fair May 27th – 29th starting at 12:00pm over at Oaks Amusement Park, 7805 SE Oaks Park Way, Portland, OR 97202, USA.

Zenger Farm will be having an Epi-pen training class at the farm on Wednesday, July 14th from 10am-12pm. Cost is $30 per person. If you want to attend send an RSVP to andy@zengerfarm.org.

And last but not least… don’t forget to SAVE THE DATE for Tour De Hives 2017 June 24-25! We will feature tour stops of backyard apiaries all over Portland. If you’d like to become a sponsor and be featured on this website, booklet, and poster please send send an email to events@portlandurbanbeekeepers.org. Tickets are going fast so head over to our website and pick up your own.