Some honeybee colonies keep Varroa destructor populations low without any chemical treatment. This model shows a patch of capped brood comb where three heritable traits work together: hygienic behaviour (detecting and uncapping infested brood), grooming (adult bees biting and dislodging phoretic mites before they enter a cell) and Varroa Sensitive Hygiene, VSH (which specifically suppresses mite reproductive success inside the cell).
The USDA's VSH breeding line and similar programmes (Suomenlahti, Bond, "Mite-Biter" bees) select queens purely on this uncapping-and-removal behaviour, and after enough generations it can hold mite loads below damage thresholds without a single miticide treatment.
A patch of capped brood comb where hygienic behaviour, grooming and Varroa Sensitive Hygiene (VSH) genetics work together against a growing Varroa destructor infestation — tune the traits and watch the mite population index rise or fall.
Open cells get capped as brood, some picking up a phoretic mite as they seal. Hygienic bees inspect and uncap infested cells before the mite reproduces; VSH suppresses how many viable daughter mites an undetected cell produces; grooming lowers the odds a cell gets infested in the first place.
Pick a colony genetics preset or drag the hygienic behaviour, grooming and VSH sliders yourself. Watch red (infested) cells spread or shrink, and track the mite population index and colony health stats as the comb cycles.
Breeding programmes like the USDA's VSH line select queens purely for this uncapping-and-removal behaviour — after enough generations of selection, colonies can hold mite loads below damage thresholds without any miticide.