Varroa sensitive hygiene

[5] It was later discovered that the factor is founded on hygienic activity of adult bees,[6][7] so SMR was renamed VSH.

Mite-infested bee pupae are removed from their brood cells, which kills any immature varroa mites present.

Bees bred to have high levels of VSH can keep mite populations below thresholds recommended for Varroa treatment including miticides.

[9] Queens from such VSH breeding sources can be allowed to mate freely with non-VSH drones, and the resulting hybrid colonies from these outcrosses will retain lower and variable but generally still useful resistance to V. destructor while retaining desirable beekeeping traits such as honey production.

[10] VSH outcrossed to commercial Italian bees recently have been shown to perform well in migratory crop pollination.