About Varroa mite of honey bees

Sugar shake test detection of Varroa mites

Varroa mite (Varroa destructor and Varroa jacobsoni) is a parasite of adult honey bees and honey bee brood. It weakens and kills honey bee colonies and can also transmit honey bee viruses. Varroa does not occur in Australia. Should it become established in this country, it will be a major problem to commercial and hobby beekeepers.

Description

Adult female varroa are reddish-brown, shaped like a scallop shell, about 1.1 mm long and 1.7 mm wide and visible to the naked eye.

Reddish-brown varroa mites

Adult males are smaller and are yellowish-white. Both sexes have eight legs.

The eggs are 0.5 mm long, milky-coloured and at first rounded.

Females of Varroa jacobsoni, another exotic species, are smaller than females of V. destructor, being about 1.0 mm long and 1.5 mm wide.

Life cycle

Varroa only produce offspring when honey bee brood is present in hives.

Adult varroa and babies

Mated female varroa enter drone and worker brood cells containing mature larvae just before hive bees cap the cells. The female varroa move to the base of the cell and submerge themselves in the larval food. When the cell is capped, the submerged mites move to the larva and begin feeding.

Individual females lay up to 6 eggs, beginning about 60 to 70 hours after the cell was capped and thereafter at intervals of about 30 hours. The first egg laid is male and all the others are female. Eggs are laid on the base and walls of the cell, and sometimes on the developing bee.

Honey bee with two Varroa mites on its thorax

Development of female varroa from egg to adult takes about 8 to 10 days. The long interval between the laying of individual eggs means that mites of different stages of development may be seen in the one cell. Protonymphs hatch from eggs about 12 hours after laying. A larger duetonymph stage occurs before the final adult stage.

The single male Varroa mates with its sisters while they are in the brood cell.

When the new adult bee emerges from its cell, the young varroa females and mother mite also leave the cell, often on the emerging bee.

An adult female varroa (oval-shape) feeds on the thorax of a developing worker bee

The daughter mites feed on adult bees and after a short period enter other brood cells to lay eggs.

The males live for only a short time inside sealed brood cells and are never seen outside the cell.

How Varroa spreads

The mites are very mobile and readily transfer between adult bees.

Varroa on pupa of worker bee

Varroa spread between colonies and apiaries when hive components, infested brood and adult bees are interchanged during normal apiary management practices.

The transport of hives, used beekeeping equipment and queen bees by beekeepers is also a very effective means of spread. In Australia, the spread of varroa is expected to be fast over long distances because of the migratory nature of the beekeeping industry.

Foraging and drifting bees and swarms can also spread varroa. In the case of foragers, mites can move from the bee to a flower and then hitch a ride with another bee or insect visiting the same flower. Varroa is not spread in honey.

Field diagnosis

Field diagnosis of exotic honey bee parasites and pests in beehives provides detailed notes on the field diagnosis of Varroa.

All stages of the mite are difficult to detect. In lightly infested colonies they are mostly found in sealed brood cells. The mites may be seen on drone and worker pupae in sealed brood cells. It is first necessary to uncap these cells and remove the pupae for examination.

The brownish-orange bumps on these bees are varroa

Female mites may be found on adult bees, especially in over-wintering colonies that have no honey bee brood. They may be found between the first abdominal segments of an adult bee where they hide between the sclerites.

Mite numbers increase slowly within a hive. It may not be until the fourth year of infestation that numbers are sufficiently high for honey bee larvae to be parasitised by several females. When this occurs, newly emerged adult bees with deformed wings, legs and abdomens may be found at the hive entrance.

Patchy brood patterns may also be seen in advanced infestations. Colonies affected to this extent will usually die.

How to test for arthropod pests such as Varroa mite and Tropilaelaps

Drone Uncapping

In colonies with large brood nests, up to 85% of Varroa mites can be found within capped brood cells, with a preference for drone brood. Therefore, uncapping drone brood (push the comb/fork of the scratcher through a patch of capped drone brood and pull a large patch of pupae out all at once) and examining pupae is an effective method for detection of Varroa mites. This method is also effective for Tropilaelaps mites, which spend the majority of their lifecycle within honey bee brood.

(Joe Riordan) Good day, this is Adam Maxwell.

I'm Joe Riordan, we're with Agriculture Victoria and we are here to show you how to do a drone uncapping today.

Drone uncapping to inspect for Varroa mite in your hives.

First step in biosecurity though is to make sure that your hive tools that you're using are washed and there's no honey or wax left on them, so you're not inadvertently moving bacterial spores from hive to hive.

The second step after that is removing the second frame from the edge, making sure the queen's not there, and resting it on the lid of the hive out of the dirt, against a super, or even up against the edge of the single box.

The next thing we're looking for then is drone cells.

I'm going to shake the bees off the frame and have a look.

It's worker cells there in his larvae put his brew laid through there and there's a few drone cells through here.

You can see the larger ones there they're elongated or if you want almost like hexa, hexagonal looking.

What we want to do is be able to pull out a number of drones so we can inspect for Varroa.

They have a, a preference to power to size and breed on drone cells because the drones, the boys are the slowest to develop.

I'll pass you that one.

What we do to do that is we use a drone uncapper or a capping scratcher stand the thing and like our hive tool we want to make sure there's no wa, honey or wax,

So we make sure that they're clean free of honey and wax.

So we're not moving any other diseases from hive to hive.

The next thing is, I'll give you that one there is thank you. Is then we put the uncapper in and we slowly tease out up our drone pupae.

If Varroa was on that, that would stand out being copper red or brown colored that would stand out on that beautiful, beautiful white flesh. Again, easing it up slowly, and you get a really good view all the way around.

In between doing a sugar shake, as we've done on this hive drone uncapping or an alcohol wash, it gives us two points of sensitivity and it gives us an opportunity to see Varroa at a couple of different stages of its life cycle.

This stage under the cap here is when they're breeding or when she's laid eggs.

The other stage is when she's on the external part of the bees.

Another important thing we don't want to cause robbing our ants to start bombarding a hive.

So we don't throw this stuff on the ground.

Some of the Bush Meat Ants take a preference to it and it can cause a bit of an ant activity around also too with bi security around American foulbrood.

All goes in a bin, and then we wash those tools at the end of at the end of that session.

And then we reassemble the hive the way it originally was with the frames in the same order and facing the same way.

And if you see anything unusual when you're doing any of these tests, please call Agriculture Victoria, or the Exotic Plant Pest Hotline.

Sugar Shake

When varroa mites are dusted with pure icing sugar, the fine granules stick to their feet and they can no longer grip the surface they are clinging to.

The dusting of adult bees with icing sugar, causes mites to fall off the bee into the white sugar. The container is shaken out (separating bees from sugar and mites) into a white bucket containing water, where the sugar dissolves and any mites present will be more easily seen.

Hi, this is Adam Maxwell and Joe Riordan from Agriculture Victoria.

We're here to show you how to do a sugar shake looking for Varroa mite exotic parasites.

First rule around biosecurity is always make sure your hive tool is free of honey and wax.

Make sure you're not moving stuff like American foul brood around.

Next step we do, good bit of smoke.

And then we take out the second frame.

We make sure that the queen's not on that frame.

No queen present.

So we pop that down on the upturned lid against the super there, out of the dirt.

And then we continue through.

And we're looking for the middle of the brood nest where parasites like Varroa would be.

What we want to do is check for the queen.

We've got our sugar shake container ready there.

Adam's just putting a bit of sugar in there.

Around about a spoonful, a tablespoon will do.

At the heart of the brood nest, we're going to shake some bees off.

And putting the frame on a bit of an angle means you get a narrower drop of it.

Just hang onto that for us.

And then if you want to do drop 'em.

And then Adam's going to pour that into our sugar shake container.

Around about 300 bees, so we don't need all of those.

But it certainly... And then the rest of them go back onto the hive.

And Adam pops the lid back on.

And then we roll them round.

What we want to do is coat the bees with the icing sugar.

It gums up the Varroa mite, their legs, and it means it's harder for them to stay attached.

And then this is called a sugar shake, not a sugar roll, and it means you've got to shake the bees.

We shake it into a bucket of water.

If there's any parasites there, like Varroa, they'll float to the top.

The sugar will dissolve. And if there were Varroa in there, they will be floating on the surface of the water.

It's a shake, not a roll.

Remember, it's a good firm shake.

And then all we need to do then is take the bees, undo that.

The bees are all okay.

And we can pour them back in onto the top frames.

As you can see, they're all alive, they're all moving around quite fine.

We then return all the frames back into it in the order they were.

And then we close the colony back up.

And if you see anything unusual when you're doing any of these tests, please call Agriculture Victoria or the Exotic Plant Pest hotline.

Alcohol Wash

Using 100ml of 25% rubbing alcohol or methylated spirits, wash 300 (1/2 cup) bees taken from the centre of the brood nest. This is a quick and effectively method for detecting the presence of Varroa and Tropilaelaps mites, as well as monitoring colony mite levels.

Hi it's Adam Maxwell and Joe Riordon from Agriculture Victoria.

We're here to show you how to do an alcohol wash to look for exotic parasite such as Varroa in your honey bee colony.

First rule around biosecurity is to make sure you wash your hive tool to remove all the honey and wax from any other hive that you've been to.

Ensure that you don't move bacterial spores from hive to hive.

Next step is we always take out the second frame from the edge, and just make sure the queen's not on there.

And we rest that on the upturned lid against the super, or if it's just single, just on the lid itself.

That's so we can be sure that we don't we don't roll the queen and that we've got room to move these other frames.

The next step is we want to get around about 300 nurse bees.

And what we're going to do is shake them onto that white paper to get them ready to go into an alcohol wash.

So we'll just go to the next frame where there's a few more bees.

Check no queen.

All right, we'll drop some of those on here.

And then we'll go to another one.

We want to get nurse bees from across the brood nest.

Check no queen. No queen present.

And just one more drop, around about three frames you should get the good coverage.

All right and we'll just go down here and I'll do another drop.

Thanks Adam.

Then what we're going to do is just put that over on the super there.

We're going to let it set, sit for a couple of minutes, and the field bees will fly up we'll be left predominantly with nurse bees.

In the meantime we can reassemble the hive so we don't stress the bees.

The next step is that we're going to I'll reassemble the hive while we're still waiting for those field bees to go.

There's none of these.

And then with the alcohol we've got 100ml of alcohol in here, the methylated spirits or 70% alcohol is okay. But metho is easy, you can get it from a hardware.

The main thing is that around a beehive, add the 100ml in before you actually approach the beehive rather than trying to get the metho and spooking the bees out - they don't particularly like the odour.

Then we're going to pour around 300 in there. That should do.

And this hive, we'll just put that to the side.

This hive doesn't have an excluder so we can pour those bees straight back into the top.

If it had an excluder you've made sure the queen's not there but just as good practice tip them in under, or at the entrance.

I'll give this to Adam.

The next step now is to upturn it, mix it and make sure that the bees are totally covered in alcohol.

It kills the bees on contact.

And then you give it a good shake.

What we want to do is dislodge any parasites like Varroa, Motal, Tropilaelaps from the bees themselves.

Give it a good shake for about 20 seconds and that should dislodge anything that's there.

Now the alcohol draws through to the bottom.

It's considered to be a more sensitive test than sugar shake, but with sugar shake you're not killing your bees.

They're both meaningful exercises, but this is a far more sensitive test.

They're both very meaningful and for people to do sugar shake or alcohol wash at home, that's very important for the industry, for hobby beekeeping and for the department.

And if you see anything unusual when you're doing any of these tests please call Agriculture Victoria or the Exotic Plant Pest Hotline.

Steps if you find or suspect presence of varroa in your apiary

It is important when varroa is suspected in an apiary that the following steps are taken by the beekeeper to reduce the risk of spread:

  1. Collect a specimen of the suspect varroa mite and place it in a small jar of methylated spirits. Keep the jar in a cool, safe place away from sunlight. Don't mail or forward any samples until advised to do so by a department apiary officer. Never take live specimens away from the apiary as this may help to spread varroa.
  2. Reassemble the opened hive to its normal position.
  3. Mark the hive with a waterproof felt pen (or similar) so it can be easily identified later. Mark the lid and all boxes of the hive with the same identification number.
  4. Thoroughly wash hands, gloves (and gauntlets), hive tool, smoker and any other equipment to ensure varroa is not carried from the apiary.
  5. Place overalls, gloves veil and hat in plastic bag and leave them at the apiary site until advised by a Agriculture Victoria Apiary Officer.
  6. Don't remove bees or any hive components from this apiary as this could help spread varroa. Before leaving the apiary, inspect your vehicle to make sure there are no bees trapped inside or on the radiator. Check the tray of the truck, ute or trailer as well. Boxes of combs and other hive material on your vehicle which bees might enter must be left at the apiary.

Varroa – a notifiable disease

If you see or suspect varroa is present in your apiary, you must report it immediately by calling the Exotic Plant Pest Hotline: 1800 084 881 (24 hours a day, every day of the year).

Notification is required by the Livestock Disease Control Act (1994). To not notify is to break the law.

Early recognition of varroa is one of the most important factors influencing the chance of controlling them and reducing their economic and social impact on the whole community.

Further information

If you require further information or assistance, please contact the Customer Service Centre on 136 186 or email honeybee.biosecurity@agriculture.vic.gov.au

Page last updated: 22 Nov 2022