Mouse Guard
Lexikon
The mouse guard closes the entrance in winter just enough that bees can pass in and out while mice stay outside.
The mouse guard closes the entrance in winter just enough that bees can pass in and out while mice stay outside. A mouse that nests in a hive over winter destroys comb, soils it, and disturbs the colony persistently.
Three designs are common: a wire mesh bent into a U-shape in front of the entrance, a perforated plate, and a mounted strip that leaves only a narrow gap open. Mesh sizes of around six millimeters are used for the wire versions, hole diameters of six to seven millimeters for perforated plates, and gap heights of about five to seven millimeters for slot closures. The figures differ by system, but they share the feature that the opening stays too small for a mouse.
Timing matters. As long as daytime temperatures still climb above about twelve degrees, the bees drive off mice themselves. The guard is fitted once the first night frosts arrive and daytime temperatures no longer exceed ten degrees for several days running, usually in October.
It is also important to remove the guard in good time in spring and to take it off before a formic acid treatment, because the hive then needs the full entrance opening.