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We are still in the process of understanding the complex relationship between Varroa Mites and failure of colonies of European Honeybees.
At first we thought they just overwhelmed a hive that is not equiped to coexist with this exotic parasite. We tried to kill all the mites in a hive by using ever increasing strengths of toxic chemicals. We soon learned that the chemicals were killing the weaker mites and creating a "super mite" that is pesticide resistant. We had to switch pesticides and the same thing happened again until we have begun to run out of pesticides and we are getting some alarmingly toxic pesticides in use in a hive that produces food for humans, not to mention the dangers of handling these chemicals.
Integrated pest management became the preferred way to deal with the pests. We use an assortment of proceedures and equipment that each take a toll on the mites in an effort to try and keep the levels of mites to where a colony can exist with the mites longer before resorting to a harsh chemical pesticide. This has proven to be a smart approach.
I use screened bottom boards which knocks down the mite population by about 10 % as that many just fall off the bees and go through the bottom board where they can not find their way back to the hive. I split my hives often, which does hinder honey production. When you split a hive, you take 3 frames of brood and bees out of an established hive and place them in a new hive. This means you took about 33% of the mites out of that hive. Then I cause the hive I am making to raise a queen of their own using eggs from the parent hive. This means the hive will be broodless until the new queen is raised and laying. It takes about 30 days from egg to egg laying queen. During this time the mites are not gaining as they can not reproduce without brood. The hive then goes full blast to make bees to fill out the new colony. The bees get ahead of the mites and both colonies end up benefiting from the split in terms of dealing with Varroa Mites. Mites are 12 times more likely to enter drone brood cells than worker cells to reproduce. This can be used against them by what is called drone trapping. Place drone sized foundation in the hive and allow the bees to draw it out. Then when the drone larvae has been capped, remove and freeze it to kill the mites as well as the larvae. Place back in the hive and the bees will clean it up. I also seek out mite tolerant stocks of bees to allow my bees to exist with a higher mite load than other bees and in fact reduce the mite load themselves by hygienic behavior.
It has become known that the mites themselves may not actually be killing the bees. The mites act as a vector for bee viruses and the virus is what the colonies succumb to. Bees naturally carry viruses in their bodies just as humans do. When under stress, these viruses sometimes emerg from dormant stage and cause disease which can kill a colony. In humans you have seen stress cause cold sores (herpes virus) to emerge and cause sores on a person. In bees these viruses cause such fatal results as K-wing. A bee that can not fly is of no use to the colony and the colony must reproduce the bee population to continue existing. Genetics will play a key role here as we find viral resistant stock. I like to leave as much propolis in my hive as possible as it has antiviral properties. I also like to look for feral bees that have managed to continue to exist. I feel that their genetics must have some influence on that fact and I want to preserve them.
This photo by Calvin Robinson was taken in one of his new package installs
As many as 7 mites exited a drone cell when a straw was used to uncap the cell. This photo shows drone larvae from a package installed about two months prior.
Photo by: Dr. Zachary Huang www.beetography.com
Mites raise and develope to different stages inside a sealed cell. They feed on the young bee larvae to provide nutrition to reproduce and grow.
Heavy infestation causes deformed bees due to feeding on them and passing viruses.
Photo by: Dr. Zachary Huang www.beetography.com
Varroa mite damage causes deformed bees which will not survive and as a result a hive dies because they can not replace aging bees. Varroa are 12 times more likely to inhabit drone cells.
Photo by Dr Zachary Huang www.beetography.com
When uncapping a cell that is near maturity, a hive with heavy infestation may have from 5 to 10 or more mites in a cell. This is not good for the larvae
Photo by Dr. Zachary Huang www.beetography.com
Yellowish color of dead Drone Pupae from Varroa infestation. Note the mites still attached
Photo Brett Butler
Varroa Mites vector viruses such as K-wing and wringled wing virus.
