lso this last weekend, I helped my brother perform a check on his bees for Varroa mites. Varroa mites are a vary common parasite that uses the bee’s own brood cycle, or the raising of their young, to perpetuate its own numbers. They are basically blood-suckers that prey on bees. Almost every hive has some of them at any time, and beekeepers should perform periodic checks to see how many mites are present in a colony. Beekeepers used to treat hives for mites quite often without first checking the degree of infestation. This led to more resistant strains of mites, and now beekeepers are encouraged to check first, treat if necessary (mite count is too high and the colony is in danger), and then re-check to see the effectiveness of the treatment. So to check the mite population, Joe found a (recipe) on the internet:
Take a canning jar, add 1/3 cup nurse bees and 1/4 cup powdered sugar.
Cap with a 1/8″ screen. Shake vigorously.
Dump any loose Varroa into a shallow dish of water with a white bottom for easy counting.
First we took apart the hive, looking for a frame with brood cells and nurse bees around them. Because the mites use the brood, or bee eggs, there should be more mites present around them on the attendant nurse bees. Right now Joe’s strong hive doesn’t have any brood cells because they apparently swarmed recently and have replaced their queen. There is at least a two week period with a queen change-over where their is no brood laid before the new queen starts. We found the ‘virgin’ queen, who’s abdomen was not yet enlarged by the laying of brood. Characteristics that distinguish her from other bees include a blacker, shinier thorax section, she is larger, and has a little more separation at her abdomen between the sections of her body. Can you find her in the picture at right? —>
Not finding brood and nurse bees, we decided to check a random sample of worker bees instead.
We filled the measuring cup with bees by shaking bees off of a frame onto a thin flexible piece of plastic, which we then curled and funneled the bees into the cup. Sounds crazy no? Then we dumped the 1/4 cup of powdered sugar on top of the screen after trapping the bees inside, and tapped it into the jar. Joe then shook the jar quite vigorously for maybe 1-2 minutes. I thought he might be shaking too hard and hurting the bees, but he said it took that much to loosen the mites. The powered sugar prevents the mites from being able to grab onto the bees with their legs, and doesn’t harm the bees. Then Joe put a half inch deep of water in the bottom of the tupperware and shook the jar upside down over top of it, and the mites fell through the screen into the water.
Below you can see the amount of mites from 1/3 cup of bees from the strong hive on the left and the weak hive on the right. All of the little red dots on the left are mites, I circled the five or so in the sample on the right.
If the mites become plentiful enough, the hive might not survive a winter. 1/3 cup of bees equals approximately 300 bees. 8% is what studies have shown a colony can survive winter with. So, if you shake out 24 or less mites from the sample, you are at or below the 8%. Joe had been seeing signs of a mite population problem, and was not surprised, but saddened to see so many. He was also surprised to see so few mites in the other hive, which he thought might be being hampered by mites. At right is a close-up of the creepy blood-suckers.
You’ll recall I said the mites use the brood cycle to hatch their young as well. Joe wondered if the lapse in bee brood during a queen change-over would cause the mite population to fall. He mused that perhaps Varroa mite populations get out of hand in hives because beekeepers prevent this natural part of wild hive’s cycle, because it decreases honey production. Beekeepers take great care so that their colonies don’t swarm and split, taking honey with them, and leaving a new queen who doesn’t start making more worker bees for some time. But perhaps the break keeps the mites in check. Joe decided to check the percentage of mites again in two weeks, and if it is still high, treat them. HopGuard is a newer miticide developed from hops that offers an alternative to agrochemical miticides, that varroa mites have developed resistances to.