In 1519, Spanish forces arrived in Mexico with weapons both seen and unseen. Between 1545 and 1550, up to 80 percent of the native Aztec population is believed to have been wiped out by disease, possibly a deadly form of salmonella.
In 1987, the varroa mite arrived in the United States with weapons both seen and unseen. In the most recent beekeeping season from 2015 to 2016, beekeepers lost an estimated 44 percent of their bees.
Coincidence? Maybe not. Some thoughts on the evolution of honey bees and varroa mites.
When Europeans came to North America, they brought their religion, weapons, and pathogens. Europe’s shift to an agricultural society happened many centuries before the natives of North America, where some natives were still hunter gatherers; and the density of people and houses in Europe was much higher as well. Over the centuries, Europe bred and passed around many germs, meaning that the Europeans’ immune systems were more robust than residents of the New World.
This is why the average 1550 Mexican native was no match for the 1550 salmonella and other pathogens that came over from Spain. While armies traveled from Europe to conquer and take over the various parts of North America, it was the unseen pathogens that devastated populations and made the native peoples weaker and easier to dominate. According to some researchers, the native population of Mexico fell from an estimated 25 million in 1519 to around 1 million a century later.
In the same way, if we somehow brought a European from the 1500’s into modern day New York City, that person would likely be no match for today’s diseases. There is a good chance they would pick up some modern deadly disease, although perhaps our current medical understanding could cure them.
So how does this relate to honey bees and varroa mites, you ask? Give me a few paragraphs….
Mites appeared in North America about 40 years ago, and since that time have been evolving their ability to resist treatments and devastate honey bee colonies. Mites directly impact colonies by disrupting the growth of pupae and weakening bees. Their unseen weapons are the pathogens they transfer directly into bees, bypassing much of the honey bee immune system. These viruses, especially the deformed wing virus (DWV), have evolved along with the mites for much of these 40 years.
A detailed discussion of this appears in Randy’s Oliver’s recent series The Varroa Problem. Randy also discusses how mites have evolved resistance to various synthetic chemicals, and have recently begun to show resistance to the current synthetic of choice, amitraz. Organic treatments like formic acid and thymol continue to be effective, although they are more labor intensive to apply and have other risks, so are not used by many commercial beekeepers.
So what about honey bees? The majority of queens in the United States are produced by large breeders that focus on gentleness, honey production, and other factors unrelated to mite resistance. While Varroa Sensitive Hygiene (VSH) bees, ankle biters, Russians, and other resistant lines of honey bees exist, the number of colonies with such queens are much smaller than the large quantities of commercial packages and queens that ship across the country every year with little or no mite awareness.
The result is that our poor honey bees are no match for the evolved mites and viruses. It is like taking Mexican natives from 1550 over to Spain. While some may survive, most of them are devastated. It is just not a fair contest. New bee colonies from standard stock can be overwhelmed by mites in their first year, much to the dismay of young beekeepers. Some beekeepers and commercial operations have reported that they must now treat their hives multiple times to keep their colonies alive. This is exactly what we would expect when mixing evolved mites and viruses with 40-year-old bee genetics.
While honey bee colonies reproduce (swarm) once or twice a year, varroa mites can produce a new generation in as little as three weeks. Mites live through the winter as part of a colony’s cluster. If we conservatively say that mites produce four new generations per year, our 40 years of evolution becomes 160 (4×40) generations of mites. Any of these generations may stumble upon new and improved ways to devastate colonies at just the right time to hitch a ride on robbing bees and move to a new colony. Meanwhile most of our honey bee queens are bred to match mite awareness of Italian, Carniolan, and other bee strains from 40 years ago.
What to take away from these musings? Two things. First, the mites and viruses are winning, getting stronger every year. If you keep honey bees, pay attention to the mites. I am not a fan of synthetic chemicals, though I have decided to use organic chemicals. If you do not like the organic approaches, perform manual treatments by splitting, providing a brood break, or otherwise disrupting the growth of mites in your hives. If your bees came from a package or large queen breeder, you are asking medieval bees to ward off modern mites and viruses. Think about how well your bees are equipped to handle varroa mites and DWV, and respond accordingly.
Second, become part of the solution. If you buy bees, look for queens bred to resist mites, whether ankle biters or Russians or other resistant lines. If you have a hive that survived the winter, split or raise new queens from these bees, to preserve the genetics and avoid buying new queens or packages. A number of wild honey bee populations have evolved to co-exist with varroa mites, so this can and will be done. It is just a matter of time and commitment from beekeepers across the country.
The more things change, the more they stay the same
Some people and places never change, despite appearances. My Facts on File Dictionary of Proverbs book says this proverb originated in the French book Les Guêpes by Alphonse Karr in 1859. It captures the notion that changes come and go, yet life stays much the same. What we perceive as significant change may not really be so significant, whether a political election, a new mobile app, or the behavior of honey bees.
I morphed the quote into the idea that mites are changing and evolving, yet on average our honey bees are pretty much as they have always been. This creates challenges for the honey bees and angst for beekeepers. As our colonies in the United States ramp up for the coming spring, let’s hope that our bees are healthy and the nectar and pollen plentiful.
May you prosper and find honey.