I started the winter with 2 NUCS (and 5 hives) – but the NUCs were dead by the end of December. Last week, I took the dead hives apart to clean them as well as to do some Crime Scene Investigation (CSI) to try to determine why the hives died.
When I opened up the NUC, I found plenty of capped stores (honey and sugar water) so I know they didn’t starve. What I also found on the bottom board was some chewed wax along with a bunch of black specs. The chewed wax was most likely from the wax cappings the bees chewed to access the stored honey. The black specs, while too small to ID with the naked eye (at least in my case). I suspected they might be Varroa Mites – one of the three biggest challenges to bee health (the other two being monoculture & pesticides/insecticides).
I collected samples, looked at them under my digital microscope, and confirmed my suspicions – both NUCs most likely died due to the weaknesses from varroa mite infestation. The sample I collected had ~20 mites in it:
As you can see from these pictures the mites are very small compared to the bee – or even a piece of mechanical pencil lead.
As I mentioned above, Varroa Mites are one of the three biggest threats to honeybee health. They are blamed for the major decline in our feral honeybee colonies. These parasites not only weaken the bee from sucking their blood, but they are also a “vector” for other diseases. The combination of the holes a mite creates in the bee’s exoskeleton along with being in a weakened state makes them susceptible to other viruses & diseases – especially ones carried by the mites such as deformed wing virus. These “other” virus & diseases is what most often kills the bees & colony.
Varroa mites are found in all hives through the US (and all countries in the world except Australia), It isn’t a question of IF you have mites, it is a question of what level of mite activity do you have. We cannot eradicate mites from the hive but must control them to a level where the colony can remain healthy. Many beekeepers use a combination of Integrated Pest Management methods and treatments to control the mites. Unfortunately, the mites have already developed resistance to some of the treatments.
Even if you do everything you can to control the mites, sometimes, events are out of your control – the latest buzz words for a mite infestation is “varroa bom”. One example is when you have a colony that is healthy, but they start robbing stores from one that has a heavy varroa load (a “varroa bom colony”). Your bees now bring home mites, causing a heavy infestation in your hive.
My guess is that my NUCs raided the hive of my “bees in the tree” after they died in early fall. (this swarm that took up residence in one of my maple trees, but died in the fall). I don’t know why the bee in the tree died but probably from Varroa since they couldn’t be treated.
Managing varroa mites in your colonies and developing varroa resistant bees is one of the biggest areas of honeybee research. I don’t think they’ll find a silver bullet to solve all of the issues, but I’m sure as we learn more, we’ll be able to manage the colonies so we have fewer losses.