We reach the end of April and the weather is still too cold for opening the hives for regular colony inspections. Although April is usually cold here in the north of Scotland, this year is exceptional with daytime temperatures not getting above 6 degrees C this week. We had a hailstorm yesterday. Yet inside the hives the colonies are developing and drones are flying. As soon as it warms up there will be an explosion of growth and swarm preparations. There will also be an explosive growth of varroa mites and we need to establish levels now and be prepared to act early in the season with a treatment if necessary.
With the help of my bee buddies Cynthia and Jane, I’ve done quick inspections to change boxes and put queen excluders between the brood boxes and shallow supers. Cynthia and I also did several sugar roll tests and were pleased that the varroa levels were less than 2 mites/300 bees. We took our sample from the brood boxes and were careful not to include the queens. The Apiary Buzz: Monitoring Varroa and More. (beelistener.co.uk)
Varroa Feed on Mature Drones.
I’ve just opened my latest copy of the American Bee Journal (May 2023, page 515) to some news that might alter how we monitor varroa in the very near future. Dr Zac Lamas and colleagues have discovered that in many locations varroa mites prefer to feed on mature drones rather than nurse bees in early spring and summer https://www.youtube.com/watch?v=GfzkreMezCI This could account for why some of us find low varroa counts in sugar roll/alcohol tests early in the season, but a big increase at the end of summer when drones are reducing in numbers. Dr Lamas has been testing samples of 40 drones using the alcohol wash test paired with traditional samples of 300 workers. At the moment, threshold levels for drones have not been established but now we know we can take this into account when planning our varroa management strategy.
Biotechnical Control.
Back to the home apiary, one colony will have a shook swarm soon because the combs are old and need to be replaced. At last, I shall be trying comb trapping on another colony. Having talked about it for a while, it’s time to get on with it. When Cynthia and I were cleaning brace comb from one colony we found varroa in drone cells so we know that that is a great biotechnical non-chemical method to reduce varroa. However, producing drones is costly to a colony in terms of energy and resources, and, besides, lots of healthy drones are needed in the drone congregation areas to provide genetic diversity for the neighbourhood colonies. Comb trapping relies on worker brood to attract and trap varroa mites and is probably less costly in the long run to a colony. It also involves confining the queen on the caged frame.
Comb Trapping.
So, what exactly is “Comb Trapping” and how does it work? It is a biotechnical/ cultural method developed during the 1980’s in Germany by Mr V. Maul. It works on the principal that female varroa mites enter brood cells shortly before they are sealed so that they can reproduce. If the beekeeper has control over the which frames are available then the varroa mite has no alternative but to enter the chosen frames that are destined for destruction before the new mites can emerge.
For beekeepers not wishing to use chemicals this is a suitable method, though efficacy can be enhanced by using oxalic acid at the end of comb trapping. Research by Buchler and Nanetti1 , for COLOSS, demonstrates a 90% efficacy for mite removal if the method is used correctly. The method is endorsed by Vejsnaes2, and Anastanov3 and is common practice in Europe and the UK. It is carried out during the period of 2-4 weeks before the end of foraging, or after a honey harvest.
How to Use The System.
On day zero, take an empty drawn fumigated comb that has already been used for brood rearing so that the queen will lay readily. You could also use an empty brood frame from the chosen colony. Mark this frame number one. Place this frame inside the isolator frame and then catch and place the queen on the frame inside the cage. This frame is placed in the middle of the brood chamber. To make space for this wider cage, remove 2 old brood frames from this colony.
9 days later, on Day 9, remove frame one from the cage and transfer the queen onto frame two and place this frame in the cage. Frame one is placed next to isolator cage in the brood nest. At this inspection, inspect the brood nest for signs of emergency queen cells and destroy any that are found.
9 days later, on day 18, frame one is removed because the cells are sealed and the varroa are trapped so this frame is destroyed. Frame 2 is removed from the isolator cage and placed beside it then the queen is transferred to frame 3 which is inserted into the cage.
9 days later, on day 27, frame 3 is removed from the isolator cage and left in the hive while the queen is released. Frame 2 and the isolator cage are removed.
9 days later, on day 36, frame 3 is removed and destroyed. The colony is inspected to check that the queen is laying normally.
The Pros:
- Up to 90% efficacy
- No chemicals required
- Because there is less brood to care for, more bees are foraging so a higher honey yield is possible
- Queen is less liked to be superseded when caged on frame and continues laying than when confined to a small cage and prevented from laying
- Realistic method for small-scale hobbyist
Cons:
- Time consuming and requires 5 visits to colony
- Requires beekeeper skill and queen handling
- Requires a timetable and relies on exact timing of manipulations
- Potential weakening of colony if applied too late in the season
- A less attractive method for commercial bee farmers
References:
1Buchler, R., Nanetti A. (2017) Seasonal Brood Interruption Study 2016/2017, COLOSS Varroa Task Force, WG2
1Jozef van der Steen & Flemming Vejsnæs (2021) Varroa Control: A Brief Overview of Available Methods, Bee World, 98:2, 50-56, DOI: 10.1080/0005772X.2021.1896196
3 Anastanov, M., (2020) Queen Trapping and Queen Caging, BBKA News Special Series Issue, Integrated Pest Management, April 2020.
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Thank you, Ann 🐝
Hi Ann
It’s cold here in Staffordshire too, although it’s about 12 Celsius. The rape is in full flower but probably not producing nectar at these temperatures. I’ve not managed to make my first inspections either. I’ve just been around the bees to put supers on everything. It needs to warm up soon or we will miss the rape altogether (which some will find a blessing). I’m assuming now that my first inspections will include swarm control so I’m making frames and preparing boxes indoors whilst the cold drizzle carries on outside.Bloody global warming! 😁
Hi Stuart,
We moved house over the winter, to the town (from the hills) where it was roughly 3-4 degrees colder than here. I’ve recently moved my bees closer to us, and been stunned by the amount of forage available (sheets of dandelions in the fields). I’m worried that I am unprepared for what is to come when (if!) the weather warms up. Frame making today again!
Jane
Hello Stuart,
I think you are right about swarm control on first inspection. There was an egg in a play cup yesterday (when the temp rose high enough and I nipped in before an April shower) but not charged with RJ.
Cross fingers for some improvement and nectar secretion for your OSR. None here this year.
Best wishes,
Ann
Nice QFT Fred! These are THE most effective ways to reduce varroa (if you have “varroa susceptible” bees.
We have had some experience of using them at Westerham Beekeepers, so a few thoughts.
There is additional flexibility of when to take off the honey as no chemical miticides are involved. That can also help with the honey yield, if that’s your thing.
Visits to the hive can be reduced to 3 (which one would probably do anyway) by keeping frame 1 in for 14 days and frame 2 for 14 days. 3 changes of the frame are not required.
On the clam style QFTs a small hole is added to the comb so she can lay both sides🙄
Hello Steve,
Thank you for those useful tips. I will remember to add the hole to the comb.
Best wishes,
Ann.
Hello Ann
Varroa and drones is an interesting topic. One of the things that always seems odd (considering that mites favour drone brood) is that you – or at least I – rarely ever see drones with deformed wings. We did some work on DWV replication in drones and it does just fine. Perhaps the extra three days kills them before emergence and they’re then discarded?
I know Wally Shaw recommends discarding the first lot of drone brood in the colony each season as it’s a mite-magnet. By the time it’s warm enough to look through my hives there are often drones present and it’s too late 🙁
Cheers
David
Hello David,
Thank you for reading the post and commenting. Yes, I have always puzzled over not seeing DWV in drones. I will check the hive entrances and floor more carefully for discarded drones. I left a shallow frame in a double brood box full of winter stores for one colony and the queen moved up to lay. The shallow frame was indeed a mite magnet. Although the sugar roll test yielded 2 varroa/300 bees there were plenty in the drone brood. I’m going to do alcohol washes on some drones to see what turns up this season. This week it might be warm enough for regular inspections!!!!!
Best wishes,
Ann