Amitraz is a synthetic acaricide used against Varroa, applied as impregnated strips or by other approved formulations.

How it works

It acts on the mite's nervous system. Applied as strips, it is distributed through the colony by contact as bees move over them.

The extended release period means the treatment spans brood cycles and reaches mites as they emerge from cells.

Advantages

• Effective where no resistance has developed
• Well tolerated by bees at the correct dose
• Not temperature-dependent
• Works with brood present, because of its duration

Resistance

Resistance to amitraz has been reported in mite populations in several regions. Its development follows the familiar pattern:

• Underdosing kills susceptible mites and leaves the tough ones
• Leaving strips in beyond the prescribed period exposes mites to a declining, sublethal dose
• Using the same active substance year after year

Removing the strips on time is not a formality — it is the single most important thing a beekeeper can do to preserve the product.

Residues

Residues and breakdown products can accumulate in wax. Testing usually looks for the breakdown products rather than the parent substance, because it degrades relatively quickly.

A closed wax cycle using your own cappings wax limits the build-up.

Rules

• Only approved products at the prescribed dose and duration
• Do not treat with supers on
• Observe withdrawal periods
• Record product, date, dose and colonies treated
• Never improvise a formulation. Home-mixed preparations give uncontrolled doses, which is both illegal and a direct route to resistance

Rotation

Alternate the mode of action, not the brand. Combining with non-chemical methods reduces how often any product is needed.

Measuring afterwards

A treatment that worked last year and does not this year is the first sign of resistance. Without a follow-up measurement that signal is missed.