Varroa Monitoring for New Zealand Beekeepers
You cannot manage varroa you have not measured. Treating blind by the calendar and hoping it worked is how hives die in autumn when the keeper thought everything was fine. Monitoring tells you how heavy the mite load is, whether it is time to treat, and crucially whether the treatment you just used actually worked. It is the backbone of keeping a hive alive in New Zealand, alongside the overall varroa picture and your treatment plan.
The alcohol wash
The alcohol wash is the most accurate common method. You collect a measured sample of around 300 bees from a brood frame, roughly half a cup, into alcohol or methylated spirits, shake to dislodge the mites, and count the mites that wash out. It kills the sampled bees, which puts people off, but it gives a clear, reliable mite count and 300 bees is a tiny fraction of a colony.
Sugar shake and sticky board
A sugar shake uses icing sugar instead of alcohol to dislodge mites from a bee sample, so the bees survive, but it is less accurate and fiddlier in damp conditions. A sticky board sits under a mesh floor and counts mites that drop naturally over a few days. It is the least invasive but the slowest and least precise. Many keepers use a sticky board for a rough watch and an alcohol wash when they need a real number.
- Alcohol wash: most accurate, sample of about 300 bees, kills the sample
- Sugar shake: bees survive, less accurate, awkward in humidity
- Sticky board: least invasive, counts natural mite drop, slow and rough
What the numbers mean and when to check
Express the result as mites per 100 bees. A low count of around one or below is comfortable, while a few mites per hundred is a clear signal to treat, and high counts mean you may already be behind. Rather than chasing a single magic threshold, the habit that keeps hives alive is checking regularly and acting early. Monitor at least in spring and autumn, before and after every treatment, and any time a colony looks off. Always test again after treating, because if the count has not dropped your treatment may have failed or resistance may be building.
Frequently Asked Questions
How often should I monitor for varroa?
At a minimum in spring and autumn, plus before and after each treatment, and any time a colony looks unwell. Letting the mite count drive your timing beats relying on the calendar alone.
Does the alcohol wash hurt the colony?
It kills the roughly 300 bees in the sample, which sounds harsh but is a tiny fraction of a hive of tens of thousands. The accuracy it gives is worth it. If you cannot bring yourself to do it, a sugar shake spares the bees at the cost of some precision.
Why test again after treating?
To confirm the treatment actually worked. If the mite count has not dropped after a treatment, the product may have failed or the mites may be resistant, and you need to know that and act before the colony is damaged.