Interactive lesson

Varroa without synthetics, step by step

Interactive lesson: measure varroa, cut out drone brood, make a broodless break, treat with acids safely and recognise American foulbrood.

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The whole lesson as text

1. How varroa destroys a colony

Varroa is a small mite that lives on bees and breeds in capped brood.

A mite on a bee — Varroa sits on a bee and feeds on it. In the brood season it roughly doubles twice a month.
Into the cell — The female enters a cell with a larva just before it is capped and lays her eggs there. The young mites emerge together with the bee.
It loves drone brood — Drone brood stays capped for 12 days, longer than worker brood. Varroa leaves more offspring in it, so it prefers it.
Signs of heavy infestation — Bees with crumpled, stubby wings, patchy brood, bees crawling in front of the entrance. August is critical, because that is when the winter bees are raised.

Why: It feeds on the bees' fat body, but does even more damage through the viruses it carries. A colony with no varroa control usually collapses within two or three years.

A colony that dies in late autumn, often with plenty of honey left, didn't "abscond". The culprit is the varroa of August.
When you see signs of heavy infestation, it is too late for gentle measures.

2. Measuring infestation

Measure varroa at least 4 times a year and treat according to the count, not by feel.

Natural mite drop — A tray under the mesh floor, with a thin film of oil or sticky paper, stays in for 3–7 days. Divide the total number of mites by the number of days.
About 300 bees — From a brood frame take about 300 bees, roughly half a cup (about 100 ml), into a jar with a mesh lid.
Icing sugar — Add 2 tablespoons of icing sugar, roll for 1 minute and shake the mites onto a white plate. The bees survive.
Work it out and write it down — Divide the number of mites by 3 to get mites per 100 bees. Write the result in the mite count log.

Why: Without measuring you don't know whether a treatment is needed, whether it worked and which colonies are more resistant. The thresholds are approximate; regular counts and comparing hives matter more.

More than 3 mites per 100 bees is the treatment threshold. 8–10 means the colony is already in serious danger.
An alcohol or detergent wash is the most accurate, but the bees die.