An issue you may have encountered as a beekeeper is the presence of laying worker bees. A worker bee can only lay drones, and therefore she cannot maintain a healthy and productive colony dynamic. Read this week’s blog to learn more about how the issue of laying workers results, how to identify the presence of laying workers and what management steps a beekeeper can take to correct the issue.

How to Identify and Manage the Issue of Laying Workers

After a colony loses its queen, and if it is unable to raise a new queen due to limited resources available (i.e. no eggs or larvae less than three days old), there is a possibility that worker bees will start to lay unfertilized eggs. Given that a laying worker bee can only lay unfertilized (male/drone) eggs the population dynamic of the colony will start to shift from worker bees to an abnormally high drone population, which is not sustainable long-term given that worker bees carry out essential colony tasks.

When a queen is present within a colony her pheromones suppress the development of ovaries in worker bees, which makes her the only reproductive female of the colony¹. Once a colony is queenless, the concentration of existing queen pheromones will gradually decrease and eventually the ovaries of worker bees have the potential to mature¹. In order for the eggs in the ovaries of workers to mature worker bees must be fed royal jelly¹. Although capable of laying eggs, workers lack the capability and anatomy to mate, which means they can only lay unfertilized eggs^1,2.

Over the past few decades there has been some research conducted on the physiology of laying workers, and how this group of bees differs from queens and non-laying workers. Researchers have found that there is greater variation in the size of eggs laid by worker bees compared to queens, with a coefficient of variance for egg length being 3.5 times higher in laying workers³. On average, it was found that eggs from queens were longer (1.620 mm), but narrower (0.368 mm) than eggs from laying workers (1.579 mm and 0.378 mm)³. In one study the development of the hypopharyngeal gland (HPG) and hemolymph vitellogenin titers was examined in laying workers to assess if their physiology was more similar to nurse bees or forger bees⁴. The researchers discovered that laying workers have physiology more similar to nurse bees compared to forger bees indicating that workers are more likely to have ovaries mature in a queenless colony earlier on in their lifespan⁴.

Generally, a colony will be queenless for approximately 21 days before a laying worker exists within the colony¹. There are a few key indicators of laying workers. To start, laying workers often lay multiple eggs per cell, and they are usually on the sides of the cell rather than the bottom of the cell². This is the result of workers having a shorter abdomen compared to a queen who can properly lay eggs at the base of the cell². Other key indicators of laying workers include a spotty brood pattern and an abnormally high percentage of drones and drone brood compared to workers².

Multiple eggs laid on sides of brood cells is a key sign of laying worker bees (© S. Camazine²).

It is difficult to locate and remove a laying worker as she is similar in appearance to other workers, and there can be many laying worker per colony, therefore, the management of this issue is not straightforward². The requeening of a colony that has laying workers is not usually successful². Frequently the colony will reject the introduced queen or queen cell if a laying worker is present^1,2.

Unfortunately, disassembling a colony is the best way to address the issue of a laying worker. If the colony shows no signs of disease, all the bees from the colony should be shaken onto the ground in the apiary, remove their hive, and the bees will drift to other colonies². There are some other suggested approaches to managing the issue, but they are not guaranteed to be successful.

The best way to prevent a laying worker is to recognize when a colony has become queenless as soon as possible, and either ensure the colony has the proper resources to raise their own queen or provide the colony with a new queen. Beekeepers should inspect colonies regularly which will help them to identify multiple queen problems early on.

References

1. Sammataro, D., and Avitabile, A. 2021. A beekeeper’s handbook: fifth edition. Cornell University Press.
2. Pernal, S. F., and Clay, H., 2013. Honey bee diseases and pests, 3rd Edition. Canadian Association Professional Apiarists, Beaverlodge, AB, Canada 68 pp.
3. Woyke, J., 1994. Comparison of the size of eggs from Apis mellifera L queens and laying workers. Apidologie, 25(2), pp.179-187.
4. Nakaoka, T., Takeuchi, H. and Kubo, T., 2008. Laying workers in queenless honeybee (Apis mellifera L.) colonies have physiological states similar to that of nurse bees but opposite that of foragers. Journal of Insect Physiology, 54(5), pp.806-812.

New Varroa Mite Treatment Product: VarroxSan

Across the globe beekeepers continue to rely on various chemical treatments to manage Varroa mites. The use of chemicals is essential for a successful integrated pest management (IPM) approach to controlling mite levels. Researchers are continually assessing the efficacy of current mite treatments, developing novel treatment formulations and applications, and working with various companies and regulatory agencies to make these products available to beekeepers. This week’s blog will discuss a new product which was recently registered by the Canadian Pest Management Regulatory Agency (PMRA).

New Varroa Mite Treatment Product: VarroxSan^TM

As part of an integrated pest management approach to controlling Varroa mites, beekeepers need to use a variety of chemical treatments and reduce reliance on a singular product. Having multiple treatment options available makes it easier for beekeepers to work different products into their IPM plan. Recently, the Canadian Pest Management Regulatory Agency (PMRA) registered a new product for Varroa mite management known as VarroxSan^TM. VarroxSan^TM, developed and manufactured by Vita Bee Health Canada Ltd., contains the active ingredient oxalic acid dihydrate (18.42%) and is administered using strips.

VarroxSan^TM strips for Varroa mite treatment (©Vita Bee Health).

As specified by the PMRA label, to treat colonies using VarroxSan^TM, a beekeeper can use a maximum of 4 VarroxSan^TM strips per 10-frame box of bees. The number of strips should be adjusted depending on the total number of frames of bees, but never exceeding 4 strips per 10-frames (see table below).

Table 1. Required number of VarroxSan^TM strips per number of frames of bees, as indicated on the product label.

Number Frames of Bees	0 – 2.5	3 – 5	6 – 7.5	8 – 10
Number of VarroxSanTM Strips	1	2	3	4

Treatment of bees with VarroxSan^TM, as with any miticide product, should only be provided after monitoring indicates mite levels are above the economic threshold (1% or 1 mite per 100 bees). To treat, the appropriate number of strips should be folded in half and hung over one comb frame within the cluster of bees. For example, this may be a singular strip placed over frame 2, 4, 6, and 8, again, considering the number of frames of bees within the box and adjusting accordingly. Strips should be hung so that the bees can walk on the strips, slightly away from the surface of the frames. Strips should be left inside the hive between 42 days to 56 days, and must be removed after a maximum of 56 days. After 42 days, strips should be repositioned to remain within the brood cluster.

To give an indication of cost, American beekeeping supply companies are selling a 60-pack of VarroxSan^TM for anywhere between $78.95 USD to $89.95 USD.  The Canadian price is yet to be determined but local beekeeping supply stores expect the product to be available shortly.

The product label indicates that VarroxSan^TM is a treatment option in spring, summer and fall, indicating that the product does not have strict temperature restrictions and is suitable for the variation of temperatures experienced throughout the Canadian beekeeping season. A main benefit to beekeepers with this new product application is that the label states that VarroxSan^TM can also be used with honey supers on. This will provide a summer Varroa mite treatment option for beekeepers who are focused on honey production.

According to Vita Bee Health, VarroxSan^TM has an average efficacy of 96.80% based on a number of studies conducted in various geographic and climatic conditions. Additionally, Vita Bee Health states that oxalic acid dihydrate, active ingredient, works as a contact acaracide that is lethal to Varroa mites, but the full extent of the mode of action is not yet understood.

It is important that beekeepers understand that VarroxSan^TM does not provide a new active ingredient to the Canadian beekeeping industry, but rather a new application of an already registered active ingredient – oxalic acid dihydrate. Oxalic acid dihydrate is already registered for beekeeper use by administering through vaporizers or the dribble method. So, if beekeepers want to use oxalic acid as part of their IPM it is recommended that they select one of the delivery methods (strips, vaporization, or dribble) and alternate this treatment with another product that has a different active ingredient (i.e. Apivar^®, formic acid, or essential oil products). There may be opportunity for a beekeeper to use an oxalic acid product more than once per season, especially if using VarroxSan^TM mid-season, but beekeepers do need to reduce reliance on a single active ingredient when planning for treatments and alternate with products containing different active ingredients.

A reminder that beekeepers should not apply more than one mite treatment simultaneously. Therefore, VarroxSan^TM, as with all miticides, must not be administered during the treatment period of any other Varroa mite treatments. Applying more than one product at the same time may interfere with the chemistry of a product potentially changing efficacy or causing harm to bees.

Overall, VarroxSan^TM provides the industry with another Varroa mite treatment option, and it is one of few that is allowed to be used with honey supers on. Now that VarroxSan^TM is registered for use in Canada beekeepers can expect the product to available for use in Canada next beekeeping season. 

Connecting with ATTTA Specialists

If you’d like to connect with ATTTA specialists or learn more about our program, you can:

visit our website at https://www.perennia.ca/portfolio-items/honey-bees/

Email attta@perennia.ca