Groundhog Day: The Varroa Problem Isn't Going Away

By: Dick Rogers, Principal Scientist/Entomologist, Bayer Bee Care Program

One of my favorite movies is Groundhog Day. In the 1993 film, Phil Connors, a cynical TV weatherman, reluctantly agrees to cover the annual ceremony in Punxsutawney, Pennsylvania. Played by actor Bill Murray, Connors awakens each morning only to relive the same day, over and over again. After coming to grips with his situation, Connors decides to use the time to learn new things, improve his life and ultimately breaks the time-loop curse, while also redeeming himself in the process.

Much like Groundhog Day, each year I find myself anxiously awaiting the effects caused by the Varroa mite on our beekeeping industry. As a beekeeper and researcher, I’ve been dealing with this deadly parasite since its arrival in North America in the late 1980s. Since then, we’ve learned a lot about Varroa and have developed hive protection strategies that have helped many beekeepers stay one step ahead of this pest. But all too often, it seems that for each step forward, we take two steps back.

Honey Bee with Varroa Virus

This is looking like it could be one of those years where colony losses are going to be high again.

Winter provides a much-needed respite for many beekeepers, but for honey bee colonies, it can be a difficult, perilous time. If hives are adequately sheltered and provisioned, honey bee colonies have a decent chance of getting through the winter with only minimal losses. But the presence of Varroa can alter the equation: Winter is a time when the effects of its parasitism really kick in. Colonies weakened by mites feeding on the developing brood, coupled with the diseases spread by this mite in the fall, often don’t have the vigor and adult bee longevity to survive harsh winter weather.

Most beekeepers expect to lose 10 to 15 percent of their colonies over the winter, but since the Varroa invasion, colony losses have more than doubled in many areas. I know an apiarist who expects losses of up to 75 percent in his state, based on his hive inspections and discussions with commercial beekeepers. He’s seen mite counts that are extraordinarily high and, unfortunately, he’s not alone. There are many more who will experience high losses again this spring, because of damage done by this invasive pest.

It seems like Groundhog Day, doesn’t it? Or as Yogi Berra said, “It’s déjà vu, all over again.”

Learning how to minimize the existential threat of Varroa isn’t easy, but it’s also not impossible. As part of my responsibilities, I oversee the management of Bayer’s research apiaries. To effectively protect and improve colony health, it is essential to monitor colonies frequently, even as often as weekly. While this seems like a heavy lift at first, there are several tools and methods available to beekeepers to make weekly colony assessments relatively fast, thorough and meaningful.

One of the most important tools to help improve bee health is the Healthy Colony Checklist (HCC), a systematic approach to bee management that is easy to use for making quick assessments. The HCC has been developed over the past several years and focuses on six critical areas in evaluating colony health: brood, adults, queen, nourishment, stressors and space. In 2016, HCC became our standard procedure (along with near-weekly hive inspections) at our Bayer research apiaries. And in each year since its implementation, we’ve seen a steady reduction in the level of Varroa infestation in our hives.

Even a well-managed system will not prevent colony losses associated with Varroa. Based on years of sampling information, we know it only takes 3 mites for every hundred bees before a Varroa treatment is recommended. And there’s not much room for error, because anything over 8 mites per hundred bees will likely result in the loss of the colony. Since Bayer adopted HCC, not only have our average mite numbers declined, but so have the number of high-infestation, worst-case situations:

Full-Year Varroa Mite Counts Chart

While using a systematic approach to assess the health of a honey bee colony may seem a bit overwhelming to some, that doesn’t make it any less essential. Most people get into beekeeping because it is immensely satisfying (certainly not because of the money). But today we’re living in a world that requires all beekeepers to adjust their management practices to address the fact that the Varroa mite is here to stay. It should be no surprise that managing bees is not the same as keeping bees.

Until a more permanent solution is found, we must continue to make the best use of the tools we have at our disposal in combating the Varroa mite. Along with the Healthy Hives Checklist, there are other great resources available in the Honey Bee Health Coalition’s Tools for Varroa Management. And our knowledge and management practices will only improve as we continue to study this pest.

Much like Phil Connors in Groundhog Day, we learn a little bit more each year about how to effectively deal with the Varroa mite and adjust our management practices accordingly. While I expect that spring 2019 will bring some reports of disappointing colony losses (possibly averaging in the 50-60% range, based on the indicators I use), there is hope on the horizon – as long as we’re willing to look for it.