There are a few ways to inspect your hive for varroa levels from observation to counting infestation rates. A 3% varroa mite infection rate (3 mites per 100 bees) is generally considered to be economically manageable. When you have more than 3% of a mite population, it’s strongly recommended to use some form of treatment. Here are some ways to observe the threat level of varroa mites in your hives.
- Drone brood culling – Putting in drone frames that will make the queen lay drone brood is a common way to lure varroa mites. The mites you want to find are the reproductive ones hidden beneath capped cells. You can destroy the brood as a removal method or attempt to count mite populations in the capped cells.
- Alcohol wash – this requires a jar, some bees, and alcohol. The standard recommendation is 70% rubbing alcohol. Scoop roughly 300 bees into a jar (or half a cup of bees – half a cup of bees = ~300 bees). You want to focus on nurse bees – varroa mites tend to prefer nurses over other workers. This is likely due to 1) how much nurse bees cluster together and 2) how close this makes the varroa mites to fresh brood. Cover the bees with enough alcohol to cover them – this will kill them, but the faster you cover them, the faster it’s over. With the wash of 300 bees, you want to shake the bees in the jar as fast and hard as you can, hard enough to dislodge mites from their hosts. After vigorous shaking, let the mites settle at the bottom and count how many there are. If you have more than three per hundred bees (so nine mites per three hundred bees), treatment is recommended.
- Sugar shake – very similar to the alcohol wash, but with powdered sugar instead of alcohol. You’ll also need a bit of #8 screen. After scooping the bees into the jar, cover the top with the #8 screen and sprinkle powdered sugar over them. Then start shaking the jar. The hope for this method is to not kill as many bees. However, this gentler method could mean less accurate mite counts. After shaking, dump the jar over on a piece of paper. This allows the mites and sugar to fall through the screen, but keep the bees in the jar. Then, count how many mites there are in the powdered sugar and eventually release the bees from the jar.
These are all methods for observing varroa mite levels in your hives. If your hives are over the threshold for varroa mites, consider some level of mechanical or chemical treatment intervention. When deploying any of these methods, be sure you are not accidentally grabbing your queen.
