HMC Bee Lab: A Year in the Life of Our Apiary

[1] Photos of our apiary site in Claremont from 2021-2022 showing how the vegetation changes across the three main seasons: Growth Season- April-June (green), Dry Season- July-October (red), and Dormant Season- November-March (orange)

Reflecting on my first year of beekeeping in Southern California

Every time I install a package of honey bees in a new hive or split a strong colony, I wonder: what sort of life will this new colony have? What threats will they face? What opportunities will they have for growth? Will they die young or live into next year, perhaps strong enough to produce a new colony? Of course, as a beekeeper and researcher, it’s my job to influence the lives of my colonies. I hope to keep them healthy through all the stresses that they face as they help us answer basic questions about bee behavior.

The importance of climate

Since hiving 10 packages of bees just over a year ago, I have had a steep learning curve, trying to decide how best to care for bees in Southern California. Before coming here to work as a postdoc at Harvey Mudd College, I learned to keep bees through experience as a researcher and hobby beekeeper in Massachusetts, Illinois, and Minnesota, especially at the University of Minnesota, where I got my PhD. Many of the things I learned while keeping honey bees in temperate climates apply here as well, but there are so many ways that the Mediterranean climate and community of plants and animals here pose different challenges. These differences affect all sorts of management decisions.

To understand why climate is important, I sometimes like to compare the life cycle of a honey bee colony to the life cycle of a perennial plant. Both of them have to start out by investing heavily in infrastructure like deep root systems or honeycomb to store food and rear new bees. This growth occurs during some limited part of the year when the temperatures are in the right range and there are plentiful resources available. They may invest a bit in reproduction during the first year, but then there generally comes a dearth period when colonies or plants have to dramatically scale back their activities and often their size, hunkering down and saving energy for the next year. If all goes well, in the second year, the efforts of the first year will allow them both to invest heavily in reproduction: the plant by producing flowers and then seeds/fruit, the colony by swarming (beekeepers simulate this by splitting strong colonies into two hives) and/or producing male bees to mate with new queens. All of this tends to follow a seasonal pattern, determined by the local climate.

Southern California Seasons

When I first moved here, I wasn’t sure what to make of Southern California seasons. They are so different from the spring, summer, fall, and especially very cold winters of Minnesota. One source that I found quite helpful is a journal article from 2017 by Park and Nieh. They wanted to understand how the pollen collection behavior of honey bee colonies changes across the seasons in Southern California (specifically San Diego County). So to start with, they looked at average temperature, rainfall, and number/type of blooming flower species during each month of the year. That analysis led them to divide the year into three periods, which they called the growth season (April-June), the dry season (July-October), and the dormant season (November-March). I have too many stories from this last year of beekeeping to put into one blog post. Instead, I’ll give a summary of the major events in each of these seasons.

The Growth Season (April-June)

Our 10 colonies began their lives in April of 2021 (you can read more about their first week here and here). My job (and I received a lot of help from Fletcher Nickerson ‘22) was to get the colonies ready to do two things. Most of them would help us answer questions about what resources honey bees deem to be worth advertising to their sisters using waggle dances, signals that convey the direction and distance to rewarding resources. So those colonies had to deal with temporarily missing a large proportion of their workers and their queen, who we put into a glass-walled observation hive and transported several miles away to the Bernard Field Station. I'm very grateful to Drew Price and the summer HMC Machine Shop student workers for building the observation hives and Gary Reuter for his advice! A few colonies also had to help us answer questions about what pollen sources honey bees in our area tend to collect. Once every two weeks, their foragers would need to enter the colony through a pollen trap that would knock the pollen loads off of their back legs. We are still working on analyzing all the video and samples we collected, but stay tuned for a future blog post about the results.

[2] Left: Three times last summer we took 3 beeswax frames with workers and the queen from 3 colonies, put them into plexiglass-walled observation hives (top photo), transported them to the Bernard Field Station, and video-recorded waggle dances (bottom photo) before returning them to their colonies. Right: We used pollen traps to collect the pollen loads collected by forager bees in our colonies. On the top you can see a pollen forager contemplating the mesh she will have to wiggle through to re-enter her hive, and on the bottom you can see the different colors of pollen brought back by foragers from one colony.

This season is when I started to learn about the food resources available to our bees. Matina Donaldson-Matasci, my research mentor, and her students have done a ton of work determining what plants honey bees are likely to collect from at the Bernard Field Station. For example, one common and attractive flower that blooms quite early (technically starting before the growth season in March) is yerba santa (Eriodictyon californicum). At our apiary site in Claremont, black sage provides another striking example. Its Latin name, Salvia mellifera, meaning the “honey-bearing sage,” seems fitting considering how much nectar the bees collect from it. At the same time at the Bernard Field Station, its cousin white sage (Salvia apiana), also attracts many bees. Later we see a surge of blooming native California buckwheat (Eriogonum fasciculatum), with its pinkish-white popcorn-like clusters of flowers, which becomes the dominant blooming species at the field station. Because of these and other plentiful resources, we didn’t need to feed our new colonies as much or for as long as new colonies in Minnesota.

[3] Honey bees visiting four species of native perennial shrubs that bloom during the growth season (April-June) near our hives

The Dry Season (July-October)

This season brings with it both brutal temperatures and very low rainfall, especially in recent years. From Matina and the LA County Beekeepers Association, I learned the vital importance of providing bees with a constant water source, which the bees use to cool their hives (read more about this at the Bernard Field Station here). I also learned about the extra precautions necessary to safely use smokers for beekeeping (avoiding Red Flag Warning days, carrying water and a fire extinguisher, etc.). Although this tends to be a dearth period for honey bees, there are some drought-tolerant native plants and watered non-native ornamental plants that attract honey bees during this time of year. I definitely noticed a decrease in both the abundance of blooming shrubs and the growth of our colonies during this time.

It turns out that climate can also have a major effect on disease transmission. One way this occurs is through effects on populations of species that vector disease, carrying it from one host to another. We humans worry about ticks and mosquitoes as vectors of diseases such as West Nile virus and Lyme disease. Similarly, honey bees face the threat of parasites called Varroa mites that vector devastating viruses from one bee to another. Varroa mites only reproduce inside the capped wax cells where honey bee larvae metamorphose (transform) into pupae and then into adults. In temperate climates, because temperatures drop and flowers stop producing pollen, the queen quits laying eggs for a long period, effectively stopping all mite reproduction. Here in Southern California the queen reduces her laying but never stops completely. That continuous source of new pupae meant that, sadly, parasitic mites could reproduce all year long in our hives here in Claremont (some beekeepers move their bees into cold storage- basically refrigerated buildings- to help deal with this problem).

[4] Diagram of how climatic conditions indirectly influence Varroa mite reproduction (and thus damage from honey bee viruses that they vector).

So I was faced with the question of when/how to control mites in this new climate. A source that I found helpful was a model, developed by beekeeper and researcher Randy Oliver based on his review of the scientific literature on mite population growth/control. It’s meant to help U.S. beekeepers estimate when to treat their colonies. It has options for different types of beekeeping operations and includes different regions. I use it with the parameters for “Subtropical colony, dry climate; no winter brood break--Southern California” (he has tutorials if you want to tailor the model more specifically). He gives a table of the likely percentage range of mites killed by each of the main available treatments, and then beekeepers can try out different treatments/times of year to estimate how well those combinations would control the mites (and prevent the colony from collapsing). Based on that model and observations of our colonies, I decided to treat with two common non-synthetic miticides: thymol in late July and formic acid in late September.

The Dormant Season (November-March)

Unfortunately, you can’t be certain of the effectiveness of a treatment or whether another is necessary without regularly checking your mite numbers. That message has reverberated through research journals and beekeeping magazines, conferences, and classes for years, but this year I didn’t take it as seriously as I should have. I checked the efficacy of the first miticide treatment, but after the second treatment, I let myself focus on other work. I convinced myself that, due to the cooler temperatures and low foraging activity of our colonies, I could likely wait until spring to treat again. In late December, I started noticing mites on my adult bees, which is always a bad sign since mites prefer to hide between the overlapping plates on the underside of bees’ abdomens. In early January, one of the colonies that had grown the fastest last year showed signs of a very heavy mite infestation. I had never seen so many mites crawling around on adult bees before. Almost all the colonies showed signs of steep population declines, probably from mite-vectored viruses.

[5] Photos from Varroa mite testing with powdered sugar- First: Find a beeswax frame full of larvae/pupae that doesn’t have the queen on it. Shake bees off the frame and then scoop 100 ml (~300 bees) into a jar with a screen lid. Second: Add powdered sugar and wait for bees to cover themselves and any Varroa mites with it. Shake the jar with the screen over a white container for one minute so the mites will fall through the screen (powdered sugar stops mites from being able to attach to bees). Third: Pour water into the container to dissolve the sugar and count the number of mites (20 mites→6.67 mites/100 bees→definitely above the treatment threshold). Finally: Return sugar-covered bees to their hives where their sisters will start cleaning them off.

[6] Colony 10 showed classic symptoms of a serious Varroa mite infestation. As the adult bees suffered from direct damage and mite-vectored diseases, they abandoned most of the larvae/pupae, which meant that the mites all moved to the adult bees (top left- mite on the abdomen of one bee; right- circled mites on many bees). The wax cells where bees had developed and then emerged also contained large amounts of white mite feces (lower left).

I rushed to treat them, fearing it was too late. I had more thymol in storage so I tried treating with thymol again, but the weather was too cool for it to have a strong effect. The colony with the worst symptoms died. After talking with Marla Spivak and Katie Lee at the University of Minnesota, I decided to switch back to formic acid. Sadly, I lost three more colonies later (overall a 40% loss, which is almost exactly the national average over the last 10 years reported by beekeepers). Thankfully, the formic acid worked for the other six colonies, which have now all recovered. In fact, during this new growth season I’ve already had to split two colonies and am getting overwhelmed with heavy boxes filled with honey!

[7] One large colony that we split into two this year. The “parent” colony is in the foreground and the “child” colony is behind it on the table with the entrance facing the other way

New year’s resolutions

We are now in a new Growth Season, and I am hoping to apply some of the lessons learned from this first year to our second year. In particular I am resolving to invest in more regular mite monitoring and treatment. A few weeks ago, I picked up three brand new packages of bees to add to our apiary. Those three colonies have healthy yellow-marked queens, and their workers are busily raising new bees and bringing in pollen and copious amounts of nectar (probably from black sage and possibly also a non-native annual plant that seems particularly common this year, black mustard). I still have so much to learn, but, with luck, these colonies will stay healthy through 2023 and help us answer questions about honey bee recruitment behavior!

[8] New queens in the three colonies made from packages of bees that we installed in hives on April 9th

HMC Bee Lab

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Wednesday, May 18, 2022

A Year in the Life of Our Apiary