Colony Collapse Disorder, the Varroa Mite, and Resources for Beekeepers

Published: July 1, 2013

There's no question that the biggest story in beekeeping since 2006 has been colony collapse disorder (CCD). Colony collapse disorder is a phenomenon in which workers bees abruptly disappear from a hive. Colony losses as high as 90% have been reported by beekeepers every year since 2006. There have been a number of agents blamed for CCD including: malnutrition, pathogens, immunodeficiencies, mites, fungus, pesticides, beekeeping practices, electromagnetic radiation, or a combination of the above. The exact cause is still unknown but most researchers agree that it is probably a combination of factors.

It has become easy and popular to blame the loss of bee hives on CCD. To be classified as CCD, there are three conditions that must occur simultaneously: there must be capped brood present, there must be food stores present that are not being robbed by other bees, and the queen bee must be present in the hive. If these conditions are not met, it is not colony collapse disorder. The fact is that most of the hive losses that do occur, especially those that occur under the watch of small or hobby beekeepers, are not due to CCD at all. There are a variety of reasons why a colony may die but most of these are related to a single pest, the varroa mite.

The varroa mite is today, and has been since the 1980's, the most serious pest of honey bees in the United States. Varroa mites will attach to bees and feed on their hemolymph, weakening the bee.

A worker honey bee parasitized by a varroa mite.

During this process the varroa mites will transmit a number of viruses to the bees, including deformed wing virus. The open wound left by varroa mite feeding also makes the bee more susceptible to a number of diseases. A weak, diseased colony will raise fewer bees and store less honey for winter. Varroa mite populations build quickly in the spring and summer causing a bee population crash and hive death from late fall through early spring, about the same time that most losses due to CCD are reported. Every honey bee hive in Missouri has varroa mite and, unfortunately, the majority of hobby beekeepers do nothing to control them.

A plastic strip impregnated with fluvalinate (sold under the brand name Apistan) was found to be very effective in controlling varroa mites. Unfortunately this product was used extensively, and often incorrectly, throughout the 1980's and 1990's resulting in a resistant population of varroa mites. A number of products containing coumaphos and thymol have been introduced since. These products have been shown to be effective but, like Apistan strips, cannot be used when honey supers are present. In addition, research and practical experience have shown that beekeepers should not rely on a single product for mite treatment. Varroa mite control should be approached from an integrated pest management (IPM) standpoint.

The first step in using IPM to control varroa is to determine whether the population of varroa mites warrants treatment (i.e. exceeds the economic threshold). University of Missouri Extension guide G7600 Beekeeping Tips for Beginners describes two methods for determining the level of mite infestation. This guide is available at every county extension office in the state. These "mite checks" should be performed monthly from March through October. If mite levels exceed the economic threshold and honey supers are not present, active controls such as Apistan, Apivar, or Apiguard (thymol) can be applied.

Many beekeepers are interested in minimizing the use of pesticides in their hives and taking a more natural approach to mite control. There are a number of strategies available that, when used properly, can be very effective in keeping mite levels low. These strategies include the use of drone cell foundation, screened bottom boards, or powdered sugar dusting. Ross Conrad's book Natural Beekeeping goes into great detail on these and other strategies for controlling varroa mites. This book is available for purchase from any of the major beekeeping suppliers. Taking advantage of honey bee genetics can also help with varroa mite. The Russian strain of honey bee has been shown to be resistant to mite infestations. Researchers in the United States have also taken advantage of a behavioral trait known as varroa sensitive hygiene (VSH) to breed entire lines of bees that are more resistant to varroa mites. Russian bees as well as VSH bees are available from most bee breeders across the country.

Keeping a colony of bees healthy is more difficult in the 21st century than it has been at any other time in history. Fortunately, the resources available to hobby beekeepers are greater than ever before. The Missouri State Beekeepers Association is an excellent source of expertise and assistance as are many of the local beekeeping associations found throughout the state. Bee Culture is a magazine geared specifically toward small and hobby beekeepers. Penn State Extension has a good online beekeeping course and many states have master beekeeper programs and/or researchers dedicated entirely to studying honey bees. The United States Department of Agriculture has honey bee research laboratories in Maryland and Louisiana. If you are looking for information regarding honey bees and beekeeping, it is out there. If you need assistance finding it, contact your county extension office.