Spring Warning: High Number of Varroa Infestations May Affect this Year's Bee Colonies

 Varroa Mites on Worker Bee
Newly emerged worker honey bee. Note deformed wings on left side, and two Varroa mites on the bee’s abdomen. A healthy winter bee can live for several months, but mites and viruses have compromised this bee’s health, meaning it probably will not live more than a few days at most.

Most of us are happy to say good-bye to cold winter weather and beekeepers are no exception. However, for many beekeepers this spring brings a renewed concern about the health of their hives. 

Cause for Concern

During the fall of 2015, Dick Rogers, a Bayer bee scientist, noted an alarming buildup of the parasitic Varroa mite in the hives he was examining. Beekeepers have struggled to protect their hives from this invasive pest since the late 1980s when it was first found in the U.S. Varroa mites weaken bees by feeding on both adults and larvae and by spreading serious diseases. Most experts consider this tiny mite to be a leading cause of colony collapse. High numbers of Varroa in the fall often lead to severe colony loss in the spring.

The amounts of mite infestation Rogers found were shocking. It only takes about three Varroa mites per 100 bees to indicate that a colony is in trouble. In many of the hives Rogers inspected, he found more than twice that amount. His years of experience told him that these colonies were almost certain to fail.  After making this discovery, Rogers quickly checked with other honey bee experts to see what they were finding and it confirmed his worst fears. Nearly all were reporting high numbers of mites.

Varroa Outbreaks Are Worse in Strong Colonies

Unfortunately, we’ve seen this all too often. A rule of thumb is when honey bees are doing well, large infestations of Varroa mites are never far behind. Varroa has caused massive colony losses before, most recently during the winter of 2012-2013. Each time, beekeepers were able to rebound by building up their colonies in the spring and summer. Keeping these new hives healthy is tough without mites, as bees face many challenges. But protecting hives from Varroa has become especially rough since the mites are prone to develop resistance, which leaves fewer treatments available.

There Is Hope

The Honey Bee Health Coalition recently released a new Varroa Management Guide, which offers beekeepers practical, effective methods of monitoring and controlling this invasive pest.  And more research is underway. Bayer is testing new varroacides, as well as more efficient delivery systems to better manage infestations. Other research has focused on the use of “smart hives” to remotely identify problems in real time so beekeepers can react more quickly, and on new genetic lines that will increase the honey bee’s natural defense against the Varroa parasite.

The end of winter brings the hope of a new season. While this spring may be particularly tough for beekeepers, we know they are a resilient group. They have overcome difficulties in the past and with the help of scientists and the many others who care about bees, they will do so again.