Learning from Nature

Source: American Bee Journal

At the recent autumn convention of Cheshire Beekeepers’ Association, Professor Tom Seeley talked about ‘Darwinian beekeeping’. I had doubts but wanted to hear the great man speak. His many years of studying honey bees, particularly those living in the wild, have surely got to be of interest to anyone keeping bees.

Pros and Cons

Seeley frequently lists the many differences between the way bees live in their natural state and those kept by beekeepers. Granted, you could do something similar with dogs & wolves or wild boar and pigs. The plain fact is that farming, whether livestock or agriculture, has advantages – such as increased yields – and costs. When we started keeping bees in hives to harvest their honey and wax, they began to divert from their natural path. Unless, of course, you accept that humans are part of nature too. Back in the day, when humans switched from hunter-gatherers to living in permanent settlements with farms, there were problems created such as increased spread of disease, and sometimes malnutrition caused by a lack of variety of foods.

Anyway, the good professor lives in a relatively unpopulated part of New York State, where most honey bees live in trees in the surrounding forests. I don’t think many places in the UK have a hive density as low as Ellis Hollow. Most bees living in trees or wall cavities likely come from swarms from nearby hives in my area. In the August 2020 issue of the American Bee Journal, Seeley published a progress report on his experiment with treatment-free beekeeping. 

Mites – it’s always mites

The thing I found most striking was the seemingly strong correlation between mite counts in October 2019 and survival to April 2020. Anything with a mite count of 9 or more (per 300 bees) in autumn was dead the following spring. Lots of mites = dead colonies. We knew that anyway, of course. Some colonies were doing something to keep mite numbers down – those were the ones that lived, and Tom Seeley would breed from. The others were inundated with mites and died. The bees that came from swarms caught in bait hives near the woods – the wild bees – did much better than VSH Italian bees from a Californian queen producer (83% survival vs 14%). The logic of natural selection is that only the colonies that can manage varroa mite loads survive. Subsequent generations will owe their existence to the union of survivor queens with survivor drones.

If you live in a remote area with wild bees nearby and are not relying on bees for your income, the ‘natural selection’ route might be attractive. Seeley advocates limiting the space available to bees to a brood box plus a super. It means they will swarm, but that’s one strategy used by bees in the wild to manage mites. The natural brood break holds back the mites in their reproduction. Imagine the chaos that would ensue if all of the beekeepers in Cheshire let their bees swarm and didn’t treat for varroa! In my patch, I can’t see it working because losses would be catastrophic.

Selecting for Super-Mites

Tom Seeley explains perfectly the risks involved and how to mitigate them: 

“If you pursue treatment-free beekeeping without close attention to your colonies, then you will create a situation in your apiary in which natural selection is favoring virulent Varroa mites, not Varroa-resistant bees. To help natural selection favor Varroa-resistant bees, you will need to monitor closely the mite levels in all your colonies and kill those whose mite populations are skyrocketing long before these colonies can collapse. By preemptively killing your Varroa-susceptible colonies, you will accomplish two important things: 1) you will eliminate your colonies that lack Varroa resistance and 2) you will prevent the “mite bomb” phenomenon of mites spreading en masse to your other colonies. If you don’t perform these preemptive killings, then even your most resistant colonies could become overrun with mites and die, which means that there will be no natural selection for mite resistance in your apiary. Failure to perform preemptive killings can also spread virulent mites to your neighbors’ colonies and even to the wild colonies in your area that are slowly evolving resistance on their own. If you are not willing to kill your mite-susceptible colonies, then you will need to treat them and requeen them with a queen of mite-resistant stock.”

Randy Oliver’s Model (again!)

I have started doing alcohol washes on my production colonies to know what’s going on in terms of mites. I don’t know many others who do this. It’s a minimum requirement for anyone considering going treatment-free, as professor Seeley says. Combining the mite counts with the Randy Oliver spreadsheet model is a fantastic way of predicting your hives’ futures. For me, treating colonies with oxalic acid in the winter when they are mostly broodless is a fundamental and necessary task. But I’m just trying to keep healthy and productive bees rather than recreate a wilderness. 

Treatments in Autumn and Winter work well on most of my colonies

I aim to get the number of mites in the hive down to 40 or less in mid-winter, which is possible with oxalic acid & broodless colonies. It doesn’t always work out, but it usually does. If I start the year with 40 mites, the bees should get through to the end of August before mite numbers get damaging. That gives me time to remove honey supers and treat (Apivar or Thymol) in September. Those two treatments, one in the autumn and one in winter, are generally all that’s needed to keep things ticking along nicely.

Starting off with 150 mites means action is needed before autumn

Brood Break

Sometimes I get a high mite count in June – something like 12 or 16 mites per 300 bees. Those colonies won’t make it if I leave them alone until September. One option is to mimic what the wild bees do. They swarm to create a brood break, but I can achieve one by caging the queen for three weeks. In the charts on this page, you can see how a colony starting the year with 150 mites will run into trouble and how a brood break in the first three weeks of July knocks the varroa back. The brood break alone seems to get the colony back on track so that the Autumn & Winter treatment get us back to the goal of 40 mites at the end of the year. This approach does leave quite a few mites in the hive in summer – perhaps 5,000 mites in a colony of 50,000 bees. It sounds high to me, but the model says it works. 

A brood break buys time, but summer mite load is high

An alternative, and one which I instinctively prefer, is to treat the hive in July straight after the brood break. This is brutal on the mites as there is no brood for them to hide in. It means that the mite levels are much lower over the summer. The model shows that you could dispense with the autumn treatment altogether. On the plus side, you can get away with just using organic acids and a brood break rather than an acaricide like amitraz. However, I wonder if leaving the bees with 3,500 – 5,500 mites over summer – by not treating straight after the brood break – would cause them to develop better defences naturally. 

Zapping the mites after brood breaks with oxalic acid

Selection Mosaics

A paper called ‘Insect societies fight back: the evolution of defensive traits against social parasites‘ by Christoph Grüter, Evelien Jongepier and Susanne Foitzik discusses a ‘mosaic of coevolution’. They say, “Social parasites are often patchily distributed, leading to selection mosaics, which can result in the evolution of host defences only in heavily parasitized locations.” Perhaps exposing bees to a level of infestation that is uncomfortable but not too damaging is the way to trigger any innate or learned defence mechanisms? I’m not sure. For any bee or larva having its innards sucked out by a giant parasite, I’m sure the choice (if there was one) is clear. My inclination is to intervene if I know that my bees have more than 2-3% infestation. It seems kinder to the bees and less risky to me. 

One thought on “Learning from Nature

  1. […] a spectrum of interventions concerning Varroa mites. There is the ‘leave them to it’ Darwinian beekeeping approach, in which many colonies will die. Not only that, they are robbed by other bees in the […]

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