Varroa mites multiply quickly, spreading bee viruses through the colony. These pests are a significant threat to honey bees if left untreated.
There is a range of effective varroa mite treatments available to beekeepers. However, the first step is learning how to identify mites at an early stage. In this guide, we provide step-by-step instructions to test for varroa mites.
Be sure to also check out our essential guide to treating varroa mites.
How do I test for varroa mites?
Beekeepers have a range of testing methods available to detect varroa mites. The most popular options are the sugar shake, alcohol wash, and sticky board drop.
1. Sugar shake method
It’s a quick and easy method that won’t kill honey bees. The sugar dislodges the mites, making examination and number counts easier.
You’ll need a jar with a mesh lid to keep the bees in.
- Pour clean water into a bucket until it reaches half full.
- Add a heaped tablespoon of icing sugar to a jar.
- Open the hive to be tested and place the upturned lid on the ground. Add a puff of smoke to help calm the bees.
- Collect a sample by shaking bees from three separate brood frames onto the hive lid.
- Scoop half a cup of bees (300 bees) into the jar and replace the lid to stop any bees getting away.
- Slowly rotate the jar for 2 minutes until the sugar has dusted all the bees. Allow two minutes, then continue gently rotating for another 2 minutes.
- Shake the sugar into the bucket of water and wait a few seconds to see if any mites float to the surface.
- Set the bees free on the ground next to the hive entrance.
Quick tips for the sugar shake method
- When shaking the sugar into a bucket, be sure to do it in a sheltered place away from gusty winds.
- Take extreme care to ensure the queen isn’t part of your sample.
- If the hive has no brood for collecting the bees, get your sample from one central comb where the bees are clustering.
2. Alcohol wash method
Although some beekeepers use this method we don’t endorse it. Why harm bees when there are other less invasive options?
- Remove the hive lid to be tested and place it upside down on the ground. Puff a little smoke to help calm the bees.
- Shake some bees from three separate brood frames onto the hive lid.
- Scoop 300 bees, about half a cup, into a wide-mouth jar and cover the top with a mesh wire lid to stop bees from escaping.
- Pour in 70% alcohol or soapy water and shake gently for one minute, then pour the liquid through a cheesecloth or coffee filter.
- Count the number of mites that get trapped in the filter.
3. Natural drop method
Varroa mites occasionally fall to the bottom of the hive. Beekeepers can insert a white grid board which helps check for varroa infestations.
- Apply a thin layer of cooking spray or petroleum jelly to the top side of a grid board.
- Insert the board under the screen bottom and leave it for 24 hours before removing it.
- Inspect the board and count the number of visible mites or other pests.
Only leave the board in the hive for 24 hours using the natural drop method. The reduced ventilation in the hive will agitate the bees.
There are special sticky liners available from beekeeping suppliers. They’re an excellent alternative to oil or other sticky substances which catch mites.
How to identify a varroa mite
The varroa mite (Varroa destructor) is a parasite that lives externally on honey bees and their brood. They have a flat, oval-shaped body similar to a pinhead (1.1x 1.7mm).
Although these reddish-brown mites are visible to the human eye, they often burrow into hard-to-see places between the bee’s exoskeletal plates.
A beekeeper shouldn’t rely on visual testing when checking a hive for varroa mites. They aren’t visible in the early stages of development, mostly living inside capped brood cells.
Symptoms of a hive infested with varroa mites
During routine hive inspections, you should check for signs that varroa mites are present. Here are some symptoms to watch out for. Use one of the above detection techniques if you suspect an infestation.
- Are bees showing signs of deformities like poorly shaped wings or short abdomens?
- Do any white larvae have red or brown spots on them?
- Can you see any mites trying to hide between the adult bee’s abdominal sections or behind its head?
- Is your hive showing signs of weakness or suffering from losses?
If you don’t see any of these symptoms, it doesn’t mean your hive is free from varroa mites. A proactive approach is essential to minimizing colony damage.
How to calculate the severity of the varroa mite infestation?
Calculating the proportion of infected bees helps the beekeeper understand how severe the varroa mite infestation is. Don’t worry – you don’t need to be a math genius to work this out!
Infestation percentage = number of mites/number of bees.
If your test reveals 3 mites and you collected 300 bees, then the calculation would be 3/300=1%
How many varroa mites are too many?
The beekeeper must make a call on whether treatment is required based on the mite count. While many bee researchers suggest 50 mites discovered in a 24-hour is too many, other beekeepers will act if they discover six or more.
Ideally, beekeepers would love their hives to have zero mites. But colonies with few mites will often keep the numbers manageable with good housekeeping. If mite counts increase, beekeepers should consider treatment options.
Why do I need to check for varroa mites?
Varroa mites are excellent at spreading viruses within hives as well as to other nearby hives. Deformed wing virus, slow bee paralysis virus, and acute bee paralysis virus are all transferred by these pests.
An infested colony produces less honey and is likelier to pick up secondary infections. It’s in the best interests of every beekeeper to check for varroa regularly.
What natural remedies do varroa mites hate?
Varroa mites are repelled by pure thyme or mint essential oils. They will fall off the honey bee and won’t come back. It is a safe way to kill mites, even if honey supers are present.
Research produced interesting results using essential oils. Testing indicated that several essential oils, notably peppermint and manuka (with a selectivity ratio, or SR, greater than 9), were effective against adult female Varroa mites while being safe for adult honey bee workers under laboratory conditions.
Oregano and litsea (SR greater than 5), along with carrot and cinnamon (SR greater than 4), also showed promising results.
These oils appeared to be more effective than thymol, a commonly used substance in beekeeping with an SR of less than 3.2. However, the practical application of these oils in beekeeping still needs to be confirmed. Source.
Powdered sugar vs. alcohol wash test
Commonly asked questions
How often should I check for varroa mites?
At a bare minimum, beekeepers should test for varroa mites in early spring and late summer. During the bee season, it is best to check your hives once a month.
What is a varroa mite test kit?
A varroa mite test kit is a simple way to test for external parasites without killing the honey bees. Although testing for parasites is possible with a few household items, these test kits include everything a beekeeper needs in one handy box.
Varroa mites are one of the biggest threats to the honey bee population. They reproduce fast and can spread viruses from one hive to another by drifting and robbing bees.
An essential part of beekeeping is testing for varroa mites. Beekeepers need to know if hive treatment is required; testing after treating a colony is vital to determine if the course of action worked.
If you’re new to beekeeping, you may also like to attend a local course or get some assistance with testing for mites. Getting it right from the outset will help your odds of managing a healthy apiary.