Most farmers across the world have been using Integrated Pest Management (IPM) techniques for decades now, even centuries, but some might not recognise it as such. Same with beekeepers. We use lots of IPM techniques that don’t involve chemicals but are really useful in slowing Varroa population growth . Currently UK farmers are being encouraged by the Government to raise awareness of IPM and talk about it more. They are supported to make their own programmes which helps to keep costs down on the farm and reduce unnecessary pesticide use. When farmers rotate crops it means that the pests feeding on one particular crop will not thrive the following year on a different one. Farmers also avoid planting in areas susceptible to pests, and they are very likely to grow tolerant or resistance varieties of crops.
What is IPM?
IPM is a systematic management approach using several methods to reduce the level of pests to one that will not injure the crop or animal. It never aims to eradicate a pest. The United Nations’ definition, as outlined by The Food and Agriculture Organisation, is “the careful consideration of all available pest control techniques and subsequent integration of appropriate measures that discourage the development of pest populations. IPM keeps pesticides and other interventions to levels that are economically justified to reduce or minimise risks to human health and the environment.”
Reducing risks to human health and the environment cannot be stressed enough. Although IPM is not against using chemicals it promulgates the prudent use of them and promotes the use of other biotechnical and management strategies. A pest is any harmful insect, plant, or disease.
The Background.
Historically beekeepers avoided using chemicals because they knew that they harmed bees, especially pesticides 1.However, when Varroa destructor (Varroa) arrived in the West in the 1980’s beekeepers found that killing sick colonies and quarantining others didn’t work well, and so they wanted a quick chemical solution. Synthetic pyrethroids were produced in profusion and pumped into colonies and we know what happened with that strategy. Over time; Varroa developed resistance to these products and more chemical treatments were produced, and so on….. Nearly everyone is aware of the current problems for human health with antibiotic resistance due to overuse and misuse. Today dangerous hospital acquired (nosocomial) infections resist treatment and compromise patient safety making some hospitals risky places to be in.
Developing Resistance.
In countries where beekeepers couldn’t afford to buy the chemicals to treat varroa, there were very high honey bee colony losses during the first few years of Varroa, but then these honey bee colonies evolved resistance and were able to live with Varroa without being weakened to the point of collapse.
We are some years behind these beekeepers but the good news in the UK and elsewhere is that some of our scientists and beekeeping leaders are promoting the journey towards treatment-free beekeeping. It is indeed a journey as followers of Steve Riley’s work know and it cannot be achieved overnight. Steve gives a detailed account of how he and his colleagues in Westerham Beekeepers’ Association achieved treatment-free beekeeping. https://www.beelistener.co.uk/beekeeping/developing-varroa-resistant-bees-steve-rileys-guest-blog/.
It was heartening to read Lynfa Davies’ “Keeping on Top of Varroa Throughout the Year” article 2 in BBKA News this month. Lynfa works for the Welsh Government as a Beekeeping Educator and has developed The Health Bees Academy which is an online learning resource for beekeepers in England and Wales, see link below.
https://menterabusnes.cymru/healthy-bees-academy/ On IPM, Lynfa says, “The good thing about IPM is that it puts us all on the pathway towards “treatment free beekeeping” and we are probably all in agreement that that is where we want to be”.
Main Beekeeping Challenge.
Varroa remains our main beekeeping challenge and we must get even smarter at managing it. The National Bee Unit has a useful booklet where you will find a template for planning Varroa control and monitoring throughout the year, https://www.nationalbeeunit.com/assets/PDFs/3_Resources_for_beekeepers/Advisory_leaflets/APHA_Managing_Varroa_2020_ELECTRONIC_ONLY-1.pdf. This will enable you to develop your own plan.
Speaking from experience, it is much easier to have a written plan to follow even if you have to change it throughout the season. Once I write down a plan I feel committed to following it. The plan is based around calendar months and mite biology. It reminds you of the testing method for Varroa, when you will test, when you will treat, and what treatment to use. It helps keep you on track, but importantly it prompts you to order up any treatments at the start of the year and saves disappointment when bee supply companies run out of stock. This has just happened here in the UK and none of the main suppliers have Formic Pro at a time when it is most needed. I’m glad that I ordered up a box of 10 treatments from Andermatt at the start of the yearhttps://andermattgarden.co.uk/.
My 2023 plan included comb trapping and confining the queen to a frame in a cage over a brood cycle. However, the weather in July has been cold and wet and brood breaks following swarm control have lasted longer than usual so I have not caged a queen. Instead, I have used these long brood breaks to good advantage and have managed nuclei to produce frames of eggs which I have used as Varroa magnets in these large colonies with no brood. Varroa are at the dispersal (phoretic) stage and travelling on adult bees until they find open brood cells to reproduce in and feed on the larvae. Varroa mites are instantly drawn to the open brood and as soon as the brood cells on these frames are sealed I remove them and freeze to destroy Varroa safely. More than 90% of the Varroa population are removed this way.
The Stage of IPM.
Before considering the different methods to use, there are several key stages in the IPM approach to know about. Think of it as continuum and keep following the cycle:
- Monitoring. This is important because if you do not monitor Varroa levels how will you know when you should treat? How will you monitor? Will you count the daily natural Varroa drop onto a sticky board below the open mesh floor? Will you remove drone brood at the pink eye stage when you can remove a forkful of 25 at a time without them disintegrating? You will need to collect a sample of 100 to have a good chance of estimating the level of Varroa infestation. Or, will you take samples of 300 bees and perform either a sugar roll test or an alcohol wash? I am a recent convert to the alcohol wash test having discovered how much faster and efficient it is compared with the messy sugar roll test which increases the risk of robbing and wasp attacks at this time of year. I count natural Varroa drop over winter. You might use an expensive contraption with cartridges of CO2 which doesn’t harm the bees but I have found that it produces a lot of moisture that makes mites stick to the sides of the container and in the mesh making counting them difficult. The small canisters of CO2 are expensive too and don’t last very long.
- Setting a Threshold. This is easier said than done but vitally important that you set your own threshold and work out when you need to treat for Varroa and with which treatment. This will depend upon many factors including; personal choice, geographical region, climate and weather, strength of colony, colony genetic traits (some colonies are more hygienic and Varroa resistant than others), colony health, and time of year. In the UK The National Bee Unit advise us to keep mite levels below 1,000 mite per colony which is considered the economic threshold; above this level the colony is at great risk. But how do we measure this level? We no longer have access to the Varroa calculator on BeeBase so we must rely on mathematical modelling and the chart on page 33 in the NBU’s “Managing Varroa” booklet. A useful tool is to study carefully the efficacy of each treatment you use. For example, with a product or technique that promises 80% efficacy levels of 1,000 Varroa mites are reached again 65 days from treatment. With 90% efficacy this level is reached again in 100 days, and with a 99% efficacy treatment the Varroa population growth is so slow that you can probably leave further treatments till next season 3. Setting a threshold for treatment also means deciding how many Varroa per 100 bees you will tolerate before treating. For example, with the sugar roll/alcohol test you might treat if you find over 6 mites (2%) in a sample of 300, or you might not treat till the level is over 3% infestation. If you test by removing 100 drone pupae and the counting mites and there are over 5 mites in the sample then you would probably treat immediately since it is predicted that over 5-10% mites will cause the colony to collapse before the end of the season3.
- Treating. This can be either chemical, biological, biotechnical/ cultural, or a mixture of these.
- Monitoring. You need to know that the treatment has been effective so monitoring is key. If there is mite resistance monitoring post-treatment should alert you. The goal is colony health.
Chemical Treatments.
Chemical treatments include organic acids such as formic, lactic, and acetic acids, essential oils such as thymol, and synthetic miticides like Apivar (Amitraz). In the UK, we can choose from a list of chemicals that are legal to use in this country but if we use the synthetic miticides we must rotate them and monitor for resistance using the Beltsville Test.
Biological Treatments.
Currently there are no known effective biological treatments but experiments are underway to find predatory mites that will harm Varroa but not honey bees. Strateolaelaps is one such beast and native to the UK. Currently it is used to control pests in horticulture and it attacks Varroa at the dispersing stage and may be useful in the future. Book scorpions, from the order of Pseudoscorpions, and nematodes have also been tried in laboratory studies. Mycelium might have more potential and a common spore forming fungus called Metarhizium is being tested from a strain that has evolved to remain active in high temperatures. It is not harmful to honey bees and might also help lower virus levels but it is still at the early research stage.
Biotechnical/Cultural Treatments.
Biotechnical or cultural treatments include good husbandry management plans that, just as with farmers, beekeepers often do automatically without relating them to IPM. These include understanding the basic biology and lifecycles of honey bees and Varroa so that signs of Varroa such as deformed wing virus, parasitic mite syndrome etc. can be easily recognised. Varroa can spread at least 8 harmful viruses across a colony so knowing what to look out for can lessen the negative impact.
Other strategies include siting an apiary carefully so that hives are spaced as far apart as possible to reduce the risk of colony drifting, disease spread, and robbing. Reduced hive entrances can also assist reducing risks of robbing and disease spread. Other apiary hygiene measures such as cleaning beekeeping equipment and PPE, and frame changing/fumigation are also relevant. Maintaining a quaratine apiary and not keeping too many colonies in one area are helpful strategies. Keep strong healthy colonies and select strains of bees that display good hygienic behaviour as demonstrated when bees groom each other and remove sick and diseased larvae quickly. We can choose to promote Varroa resistant bees which uncap and recap brood cells to disrupt mite breeding cycles.
Using open mesh floors can offer 50% efficacy in removing varroa from a colony but if used alone they are not very effective. This is why IPM relies on using several different biotechnical methods which reduce the reliance on strong chemicals such as the synthetic miticide Apivar which eventually will become less effective over time. Performing an artificial swarm and using a frame of open brood to trap Varroa has an efficacy of 90%. We can trap queens for a cycle and cause brood breaks and we can remove drone brood for a couple of cycles being careful to remove the frames before the mites emerge. Drone removal is effective at removing mites but drones are costly for a colony to produce, and they are also important for genetics and colony health.
I hope that this helps you plan your Varroa management in a useful way so that your colonies are evern healthier next season. I’m busy doing alcohol washes on all 9 colonies during this last week of July so that they can have the best chance of producing healthy winter bees and making it through winter.
References.
1 Caron, D,M. (2021) Time to Control Mites, American Bee Journal, September 2021 pp. 959-963.
2 Davies, L. (2023) Keeping on Top of Varroa Throughout the Year, BBKA News, July 2023, pp. 232-234
That was such good informative advice on varroa management Ann. So helpful and interesting. How true about the comparison between humans and antibiotics. When bees are given time to build up their resistance and establish a robust immune system then stronger colonies will usually emerge. Unfortunately for some bee keepers they want a quick fix especially I would imagine bee farmers. It’s riding the storm really like Steve Riley and their bee keeping association.
Thank you for commenting, Susan. The root of the problem is probably the lack of understanding about how resistance develops. There seems to be a better general public understanding now that this problem affects humans in such a big way. Anyone who relies on beekeeping for an income doesn’t want to watch their stocks die of disease and wait several years for them to build up again. There is so much pressure to supply the market with honey that it is not so easy to do this. The bee farmers that I know are all very much into animal welfare and looking out for disease. In fact, they are much more aware than the average hobbyist is about the foulbroods and how to prevent spread. They are not all using synthetic pyrethroids and many are using organic acid Varroa treatments.