Drone brood lead to more Varroa
I have a question regarding the consequences of your answer regarding flooding an area with drones (December 2024 Classroom). Letting the drone brood, especially multiple generations of drone brood, hatch will very negatively affect a colony’s Varroa population. How would you recommend countering this issue? I was trying to do exactly this in a local area, with the associated spike in Varroa population, and had to take remedial measures that negatively impacted my honey crop.
Calum Grigor
Germany, November
A
You are 100% correct! Using drone comb to produce more drones for mating purposes will almost certainly result in higher Varroa populations in the colonies in which you place the drone combs. We know that Varroa prefer to reproduce in drone cells rather than in worker cells. Drone brood is attractive to Varroa, and mites produce more offspring per cell invasion when invading drone cells rather than worker cells. The latter likely has to do with the fact that drones take ~3 more days to develop from egg to adult than do workers. This gives Varroa more time to get more of its female offspring to adult maturity prior to the adult bee emerging from the cell.
This, then, seems to produce a recommendation (use drone comb when you want drones available to mate with queens) that is destined to lead to the production of more Varroa and an increased chance of colony collapse. This is, in fact, the case. So, what should one do about this? You want good drones when you are producing queens. However, should you use drone comb at the risk of increasing your Varroa populations?
At the risk of sounding trite: You must do what you must do. If you are in the business of producing queens or want to improve queen-mating success/genetic diversity, you can increase the number of drones in your hives by adding a frame of drone comb. Commercial queen producers do just that. They select stocks of bees for queen-grafting purposes, but they also select and augment stocks of bees for drone production purposes. They, then, must deal with the Varroa consequences. They do this all the standard ways one would address Varroa even if they were not in the queen production business. They monitor Varroa populations using conventional methods (alcohol washes, powdered sugar shake) and treat for Varroa when those populations exceed an economic threshold (usually around 3 adult mites/100 adult honey bees).
Using drone combs will cause colonies to reach those Varroa thresholds more often than when not using such combs. Correspondingly, this means that beekeepers will need to monitor and treat for Varroa more often when using drone comb than when not using it. The good news is that the two management strategies (wanting to produce good drones using drone combs and wanting to limit impact to Varroa) are not mutually exclusive. You can accomplish both goals, but it will take more prudence.
You mentioned an obvious downside to using drone comb. Your colonies had more Varroa, and you had to step in during honey production season and treat your colonies. You state that this led to a loss of honey crop. Unfortunately, this is some of the collateral damage associated with using drone comb. However, I maintain that it is possible to use drone comb to augment drone populations in an area, while remaining vigilant to control Varroa in a manner that would not compromise your honey crop. You would simply need to manage Varroa around the honey flow.
For example, you discovered that using drone comb led to Varroa populations that exceeded the economic threshold during the honey flow. Now you know this. Next year, then, you can take different Varroa control approaches before the honey flow arrives, approaches that will allow you to forgo treating during the flow. For example, you could use drone comb before the flow and couple that with a treatment of oxalic acid (according to label). Then, you get drones and reduced Varroa populations. During the flow, you can forgo the use of drone comb altogether. This would reduce drone production, but it would only be during the honey flow.
In conclusion, using drone comb will likely lead to the production of more Varroa. If your goal, though, is queen production, you will need to use it anyway and be diligent to manage Varroa.
Oh, and thanks for reading this in Germany!
Resources on Varroa Control
I attended the ISBA (Illinois State Beekeepers Association) convention in Springfield last month (November). Both of your sessions were very informative. During one of your seminars, you shared a few website links to aid in Varroa treatment. I thought I saved this information, but I cannot seem to find it. Any possibility of pointing me in the right direction?
Josh Bell
Illinois, December
A
I would be happy to share the resources with you. I really love the Varroa control resources produced by the Honey Bee Health Coalition. You can find those resources here: https://honeybeehealthcoalition.org/resources/varroa-management/. You will find four amazing resources at this website:
- Varroa management guide — This is a PDF you can download to find the latest information on controlling Varroa. It includes information on monitoring Varroa populations, various treatment options, treatment efficacy, and seasonal control strategies. To me, it is the single best document ever written on Varroa control. It truly is a wonderful resource.
- Varroa videos — There are 12 videos on Varroa control available on the website. The videos are a complement to the management guide. They are, in effect, the video version of the guide. The topics are the same ones covered in the guide. They reinforce what you learn in the guide and are helpful for visual learners.
- “Host an Evening Varroa Bee Club Program” — This is a recorded presentation that you can download and show to your local bee club. The developers designed the presentation with local bee clubs in mind. The authors of this video developed it as a complement to their other offerings (the management guide, the 12 videos, and the other content).
- Varroa Management Decision Tool — This is an interactive tool that helps you decide (1) if you need to treat for Varroa and (2) what options will give you the best results based on the status of your colony. I love this tool. In fact, I have used it many times in front of live audiences, showing how it helps one decide when and how to treat for Varroa. The developers designed the tool to assist you with rotating control strategies so that Varroa do not become resistant to any one strategy.
I also recommended an additional resource during the referenced meeting. Dr. Cameron Jack (University of Florida) and I published a review article on Varroa Integrated Pest Management. You can find it here: https://academic.oup.com/jinsectscience/article/21/5/6/6372257. In this article, Dr. Jack and I reviewed the world’s literature on Varroa control and summarized the work in a single document. We even provide, toward the end of the document, a decision support tree to help you determine when and how you should treat for Varroa. We originally wrote it with scientists in mind. Our idea was to prompt more research on this topic. However, we wrote it to be very beekeeper friendly. I think using the information produced by the Honey Bee Health Coalition and reading the document Dr. Jack and I wrote will give you a leg up in your efforts to control Varroa …
