Varroa mites are the bane of any beekeeper’s existence. These debilitating parasites stop honeybees from producing honey, which can be crippling for any honey farmer or even those who practice beekeeping as a hobby. Let’s find out all about how to prevent varroa mites in your honeybee colonies.
What Are Varroa Mites (Varroa Destructor)?
The official name for varroa mites is varroa destructor. These external parasitic mites attack and feed on honeybees, Apis cerana and Apis mellifera, causing disease in the bees called varroosis.
The mites reproduce in honey bee colonies and attach themselves to the body of the bee, weakening it by sucking fat bodies, which is dynamic insect tissue for lipid and nutrient storage.
What Do Varroa Mites Look Like?
Varroa mites have a red-brown color. They have an oval, flat shape and range in size from 1.1-1.5 mm. Because of their similar color and size, varroa mites are often confused with the braula fly. (Braula coeca).
Can You See Varroa Mites on Bees?
You can absolutely see varroa mites on bees. They attach to them like tiny ticks. Varroa mites can be seen by the naked eye and are the size of a pin-head on the bee’s body. If a bee was as big as a human, that’s like having a mite the size of a dinner plate!
The crab-like mites attach themselves to adult bees, pre-pupae, and pupae, piercing the skin and feeding on their blood (hemolymph fluid) and fat.
Since they bring about diseases, it’s the viruses that the mites transfer that are the main issue and not necessarily the mites themselves.
Where Did Varroa Mites Originate?
These mites were originally a pest of Eastern honeybees. But those bee populations have built up a tolerance to the mites and have developed ways to keep them under control so they can coexist.
However, Varroa destructor mites have made their way from Asia to other parts of the world (with the exception of Australia) and western honey bees have not developed a tolerance to them as their Asian counterparts have.
The mites were first noticed in 1987 in the USA and in 1992 in Britain and have wreaked havoc on colonies ever since.
Image credit: Science.org
Why are Varroa Mites a Problem?
According to the National Academy of Sciences Journal, the mite species is a vector for several debilitating bee viruses such as RNA viruses like deformed wing virus (DWV).
Infestations can spread from hive to hive via foraging worker bees with Varroa mites attached to their bodies.
Since varroa mites are attracted to the larvae’s scent, they can get into brood cells before the bees cap them. Then, they are able to feed on developing bees in the cells, laying eggs and reproducing.
These mites definitely sound like an unstoppable force from a horror story but they can be stopped.
How Can I Tell if My Bees Have a Varroa Mite Infestation?
During routine inspections, you’ll want to check for Varroa mites.
There may be a problem if you detect the following:
- Reddish or brown spots on the larvae
- Bees with deformed wings
- Bees with growth issues
- Varroa mites (pin-prick sized) on adult bees (indicating heavy infestations)
- Bees not surviving past autumn (can be avoided if treated on time)
An easy method for detection is to use a clear one-pint jar with a lid made from mesh (#8 mesh hardware cloth). A mason jar works well without the sealing band and you can fit the mesh over the jar and put the screw ring/metal screw band back onto the jar. Or, if you want more specialized equipment, you can use this Varroa Easy Check plastic container.
Shake around two hundred to three hundred adult bees (which will look like around half a cup of bees) from your frame with emerging brood into the jar. Close the mesh lid. Make sure when scooping up your bees, you don’t accidentally take the queen.
Next, add two to three tablespoons of 6x powdered sugar (without added corn starch) through the mesh lid.
Set the jar aside to allow the bees and mites to be covered with sugar. Bees will start grooming themselves once covered in sugar which will dislodge the mites and the sugar will stop the mites from having a good grip on the bees’ bodies.
Shake the sugar out of the jar onto a clean, flat surface through the top of the mesh lid. A white surface will work best.
The bees will not be killed (if you’ve been careful) – but may be agitated from being shaken – and can be returned to the colony. You may want to wait until they’ve calmed down before returning them to the hive.
Using a magnifying glass, if you see ten or more mites per your two-hundred bees, you need to treat your bees.
Here’s a previous post we have written about how to check your hives for mites.
How to Stop Varroa Mites
There are different veterinary-approved treatments available such as Apistan, Apiguard, Apivar, VarroxSan and others.
Please use gloves when you use these products for treatments.
Please note you shouldn’t treat your bees during honey flow or when supers are on the hive.
Here’s a quick, eight-minute step-by-step video of how to treat your bees for mites.
https://www.youtube.com/watch?v=uhnb8IsvyRE&ab_channel=DadantBeekeeping
When to Treat For Varroa Mites?
Treat in March before supers are added. Treat in August or September when the supers have been taken off (after you’ve completed honey extraction) and treat at the end of December or at the start of January with oxalic acid.
How Do I Prevent Varroa Mites?
Preventative measures for mites require understanding the level of mites in your colony, understanding what mite level is safe, and keeping the mite population low with treatments.
The safe level of mites will depend on your bees’ tolerance. Monitor your colonies and record their levels and see how they survive. If they are not thriving, then the mite level is too high and that’s your threshold, but thresholds can evolve over time and bees can become more resistant and tolerant. A general rule is that a 3% infestation where you see under nine mites per three-hundred bees is a “safe” level.
How to Get Help From Dadant & Sons With Varroa Mite Treatments
At Dadant & Sons, beekeeping is in our blood. Mites are one of those pesky problems we all have to face. We sell multiple products to help control your mite populations – from mite screens to medications and more.
If you have any questions about our products and how to use them or need advice on preventing varroa mites, don’t hesitate to contact us.