How to check for Varroa mites? - briefly
Collect a sample of roughly 300 adult workers, add powdered sugar, shake for one minute, then count the mites that fall through a mesh screen; alternatively, crush a known number of bees in alcohol and examine the liquid under a microscope to calculate infestation rate.
How to check for Varroa mites? - in detail
Detecting Varroa destructor in honeybee colonies requires systematic sampling and observation. Reliable results come from combining several diagnostic techniques, each targeting a different stage of the mite’s life cycle.
A common field method involves placing a sticky board beneath the hive for 24 hours. The board captures mites that naturally fall from adult bees, providing a drop count that reflects colony infestation. Count the dead mites, divide by the number of days, and compare the result with threshold values (e.g., > 3 mites per day indicates a serious problem).
The sugar‑roll assay offers a rapid estimate of mite load on a sample of adult workers. Collect 300 bees from the brood nest, place them in a jar, add powdered sugar, and shake for one minute. The sugar dislodges mites, which fall through a mesh into a collection tray. Count the mites and calculate the percentage (mites ÷ bees × 100). Values above 2 % generally require treatment.
Alcohol‑wash sampling provides the most accurate quantitative assessment. Remove 300 bees, immerse them in a jar containing 70 % ethanol, and agitate for one minute. The liquid releases attached mites, which settle at the bottom. After decanting the bees, count the mites and compute the infestation rate as a percentage. This method destroys the sample but yields precise data for management decisions.
Direct visual inspection of brood cells can detect reproducing mites. Uncap a section of sealed brood (approximately 100 cells), examine each cell for the presence of a mite or its offspring, and record the proportion of infested cells. A brood infestation rate above 1 % signals the need for intervention.
Regular monitoring schedules improve early detection. Conduct sticky‑board or sugar‑roll assessments at least monthly during spring and summer, when mite reproduction peaks, and reduce frequency in winter when colonies are less active.
Record all results in a logbook, noting date, colony identifier, method used, and calculated infestation level. Consistent documentation enables trend analysis and informs timely treatment applications, minimizing colony losses caused by Varroa.