The varroa mite is a real problem for honey bees. Most beekeepers manage it with treatments, and so do we. But we do not think anyone wins the fight against varroa with treatments alone. The plan is the bee. This page explains what the mite does, why breeding matters, and how we select colonies that keep their own mite numbers down.
What varroa is
Varroa destructor is a mite that lives only on honey bees. It cannot survive on any other host. It feeds on adult bees and on developing brood, and it hits the brood hardest.
The mite is only part of the problem. It also carries viruses from bee to bee. Dr. Nurit Eliash of the Shamir Research Institute at the University of Haifa has studied varroa for about 17 years. She describes a three part system: the bee, the mite, and the viruses. The viruses and the mites together are what bring a colony down.
Why our bees have no defence built in
Varroa did not start on our bees. Its original host is the Eastern honey bee, Apis cerana, in Asia. The two lived together for millions of years. On that bee, the mite can only reproduce in drone brood.
The bee kept in Canada is the Western honey bee, Apis mellifera. It does not have that long history with the mite, so it has not learned to cope. On our bees the mite breeds in worker brood too, and worker brood is most of the brood in a hive.
How fast mites build
A mite only reproduces inside a capped brood cell. Worker brood stays capped for about 12 days. Drone brood stays capped for about 15. The longer cap gives the mite more time, so mites do best in drone cells. Mites are stoked on drones.
Count the whole life and the gap is plain. A drone takes 24 days from egg to adult. A worker takes 21. A queen takes 16, which is so fast that mites can hardly breed in a queen cell at all.
A mother mite can raise two or three daughters in one drone cell. Dr. Kirsten Traynor directs the State Institute of Bee Research at the University of Hohenheim in Germany. By her count, the mite population can triple or quadruple every 15 days through the drone season.
Late summer is the danger point. The colony stops raising drones and the brood nest shrinks. The same mites crowd into fewer cells, and several mites end up sharing one.
Why treatment alone is a treadmill
A honey bee colony reproduces about once a year, when it swarms. Mites breed again and again in a single season. Each round is a test the mite can adapt to, so the mite adapts far faster than the bee. Mites have grown resistant to one synthetic treatment after another. Dr. Traynor calls it a “chemical treadmill.”
There is a second cost. Bees that are always treated never get the chance to adapt. In Dr. Eliash’s words, “breeding must be the base for coping with Varroa mite.”
Most treatments also cannot reach the mites inside capped cells. Formic acid is the exception, because it moves through the hive as a vapour.
What resistance looks like
Resistance is not one trait. It is a colony that keeps its mite numbers low through a summer, on its own.
The trait we test for is varroa sensitive hygiene, or VSH. Worker bees sense that a capped cell has a mite in it. They open the cell and clear it out. That breaks the mite’s breeding round before her daughters mature.
Hygienic behaviour is the wider habit behind it. A hygienic colony finds sick or dead brood and removes it fast.
How we select
We count. We monitor our colonies for mites from spring to fall. A screen under each hive catches the mites that drop, and we count them.
We treat twice a year, and only with organic treatments. Formic acid and oxalic acid, in spring and in fall. The summer in between is the test.
We keep the colonies that hold mites down. Those become next year’s breeders. A colony that cannot keep its numbers low leaves the breeding program. Any colony with disease is culled.
We breed under heavy mite pressure. Our yards are full of drones on purpose, because good drones make good queens. Drone brood is also where mites breed best. A colony that keeps mites down in a yard like that has earned its place.
We select both halves. We keep designated drone mother colonies alongside our designated breeder colonies. Our queens mate here, so the drones they meet come from selected stock too.
We test. We test for VSH traits every year. We also send queens to the National Bee Diagnostic Centre each year for sperm count, sperm viability, and virus screening.
We wait. A breeder queen must come through at least two winters here before we graft from her.
We look at the whole colony. Mites are one trait of several. We also select for early foraging, heavy pollen stores, propolis collection, overwintering success, and low disease.
What it does not mean
No bee is mite proof. A queen from selected stock is a head start. She is not a reason to stop looking.
Count your mites, and keep counting. Going without treatment only works for beekeepers who monitor closely.
We are still learning. That is what we love about beekeeping.
Where to go next
Our queen bees page covers the stock, the testing, and the university research we take part in. Queens ship across Canada from early May to about August 10.
Want the colony as well as the queen? See our nucleus colonies.
Sources
Ellis, J., & Vu, A. (Hosts). Varroa biology, evolution and control with Dr. Nurit Eliash (No. 242) [Audio podcast episode]. In Two Bees in a Podcast. University of Florida Honey Bee Research and Extension Laboratory. https://entnemdept.ufl.edu/honey-bee/podcast/
Ellis, J., & Vu, A. (Hosts). Varroa biology and pesticide research with Dr. Kirsten Traynor (No. 248) [Audio podcast episode]. In Two Bees in a Podcast. University of Florida Honey Bee Research and Extension Laboratory. https://entnemdept.ufl.edu/honey-bee/podcast/
Our own selection methods are described by Emily Huxter of Wild Antho, October 2026.