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Where this comes from. The doses and temperatures below are Vita’s own, from the Apiguard frequently asked questions revised October 2021. Apiguard is the thymol product most people in the UK use, so it is the worked example here. Always read the leaflet that came with your pack, and follow that. Sources at the foot of the page.
The August varroa treatment, and why it is the one that counts covers when and why. This page is the practical bit: where the tray goes, what to do about heat, and how the dose changes on a double brood box.
Make room first
A tray of gel sitting flat on the top bars with a crown board pressed onto it does nothing, because the bees cannot get to it. Vita ask for a spacer (an eke) or preferably an empty super on top of the brood chamber. 1
Peel the lid back, put the tray on the top bars gel side up, and close up. One 50 g tray per 10 frames of bees.
The empty super you put on for this is the same box the feeder goes in next month. Setting up to feed has the detail.
Temperature
Apiguard needs the outside temperature above 15 °C. 1 That is not because the gel needs warming. The bees spread it around the hive while they are trying to clean it out, and they only do that properly when the colony is active.
It works better the warmer it gets, up to about 40 °C. Which is what makes the hot weather advice cut the dose rather than raise it.
Put it on in the late afternoon or evening. It is cooler, the bees are home, the gel gives off less vapour to begin with, and the colony gets used to the smell gradually rather than all at once.
The question that comes up most. “It is too hot. Can I halve the dose and give it three times, two weeks apart?”
Almost. Vita say that above 25 °C you can use a half dose and still get a very good kill: 2 doses of 25 g, one week apart, instead of 2 x 50 g two weeks apart. A third 25 g dose is sometimes used after the second week where mite infestations are high.
So the halving is right and the third dose is right. The gap is one week, not two. And the total goes down, not up: 50 g, or 75 g with the third dose, against 100 g for the standard course. The heat is doing the work, so less product is needed. Treating harder in hot weather is the mistake this advice exists to prevent.
Hot weather, in full
When it is very hot the thymol comes off the gel faster and the bees are more active moving it about. Both make the treatment stronger, which is why less of it is needed. 1
Two things matter more than usual in the heat:
- Do not restrict the entrance. The thymol vapour has to be able to get out. Several of ours run underfloor entrances reduced with sponge, and the sponge comes out while the trays are on. This runs against the wasp advice for the same time of year, so if you have a colony that needs its entrance reduced, watch it closely while the treatment is on.
- Give the hive good ventilation.
Vita also sell 25 g sachets in some countries. Above 25 °C on average, a course of 2 x 25 g or 3 x 25 g per 10 frames of bees works, and a fourth 25 g dose can be applied where infestation persists. Same principle, more flexibility.
Store the unused product below 30 °C and out of the sun. It starts to separate at about 38 °C and may not recover, even with stirring. Do not leave it in the car.
Single brood box
The straightforward case. One 50 g tray on the top bars, empty super above, close up. Second tray after 2 weeks, left in place for another 2 to 4 weeks. The ideal treatment period is 6 weeks in total. 1
Double brood and brood and a half
This is where most people get it wrong, and it is not obvious. There are more bees to reach, so a higher dose is needed, and it goes in two places. 1
- Most of the bees, brood and varroa will be in the lower box. Put the 50 g tray on top of the lower brood box’s frames.
- Put the second brood box on top, so the tray sits between the two boxes. Make sure there is still space for the bees to get at the gel.
- Thymol vapour is heavier than air, so it will not travel up on its own. Add a reinforcement dose of just 25 g on top of the second brood box.
- Repeat the whole thing after 2 weeks.
Do not put more than 25 g on the top box. Vita are explicit that more than that can lead to excess thymol vapour down in the lower chamber. More is not better here.
Bear in mind that Vita do not quote a separate control figure for double brood. The higher dose is needed, simply because there are more bees to reach. Worth knowing when you read the mite drop afterwards.
Nucs and small colonies
A 50 g dose is too much for a small colony, and the consequence is not just waste. Colonies of under five frames may not tolerate it, and the workers may start throwing brood out. 1
- Nuc or small colony: 1 x 25 g, second application 2 weeks later. A third 25 g only if mites persist and they took the first two well.
- Smaller nuc again: halve it again, to about 12.5 g.
What is normal, and what is not
Normal:
- The gel vanishing in a few days. It can take anywhere from 2 to 10 days to go, and it depends on temperature and on the colony. Do not put the next dose on early. Wait the full 2 weeks. 1
- The second dose lasting longer than the first. By then they are used to the smell and are less bothered about cleaning it out.
- Bearding at the entrance. Bees beard when the hive is too hot anyway, and they sometimes do it when Apiguard first goes on in warm weather. It is usually temporary and it is rare for them to abscond. What a beard actually means covers telling it apart from swarming and from robbing.
Not normal, and act on it:
- Brood being thrown out of the entrance. Some strains are more sensitive to thymol, and hygienic bees can fail to recognise brood under the smell and remove a patch of it. If you see this: take the Apiguard out and feed the colony. Check the dose matched the size of the hive, and that the entrance is not blocked. If it has been a repeated problem, use a non-thymol product next time.
Treat the whole apiary at once
Treating one colony and not its neighbours does not work for long, because mites come straight back in on robbing and drifting bees. 3 Treat everything on the site in the same week.
Supers, honey and the paperwork
No supers on, and not during a flow. Thymol can taint honey. 1 Take the crop off first: getting the bees out of the supers.
A varroacide is a veterinary medicine. Use it according to its instructions, and write down what you used, on which hives, when, how much, and the withdrawal period. 2 That record is a legal requirement and has to be kept for five years. The beekeeper’s veterinary medicines record sets out exactly what goes in it.
Monitor before you treat and again afterwards, so you know whether it worked rather than assuming. 3
The short version
- Empty super for headroom, tray gel side up, one 50 g per 10 frames of bees.
- Above 15 °C, in the evening.
- Above 25 °C: 2 x 25 g, one week apart, optional third. Less product, not more.
- Double brood: 50 g between the boxes plus 25 g on top, and no more than 25 g up there.
- Nucs get 25 g. Smaller nucs again, about 12.5 g.
- Brood thrown out means take it off and feed.
- Whole apiary at once, and write it down.
This guide is general information, not legal advice. Rules change - always check the current guidance on GOV.UK before relying on it.