Varroa Mites - A True Community Problem

APIS Information Resource Center

Many beekeepers are individualists. Experience trying to get beekeepers to act in unison reveals at best a laissez faire attitude about cooperating together on certain projects. In fact, the history of associations and other groups dedicated to beekeeping issues more often than not shows that beekeepers actively work against each other. Evidence from seminars and other educational events also supports the thesis that beekeepers are content to go about their business independent of their neighbors.

To non beekeepers, the individuality of many beekeepers seems strange, for honey bees are just the opposite. They are the most social of creatures. A single individual in a beehive, be it queen, drone or worker, means nothing. Survival depends on working together for the common good. If this is a good strategy for bees, then why do beekeepers not subscribe to it?

In the past, the rugged individualistic beekeeper could function well enough. In fact, the craft demanded one be a self- starter and an innovator. Times were simpler (or seemed so) and there were fewer non beekeepers with whick to interact. Advances in transportation and increases in growth and development have affected rural and urban areas. This has resulted in problems often associated with activities of other people. For the beekeeper, this has meant everything from death of colonies because of pesticide application to permanent loss of beehive locations.

In 1987, Varroa mites were detected in the United States, forever changing the face of beekeeping. Fortunately for U.S. beekeepers, a technology was in place to deal with the Varroa mite, a parasite that effectively kills most honey bee colonies it invades. Certain chemical control methods were legal and labelled; they reduce mite populations in beehives by over 95%. It is important to understand, however, that although chemicals control the mite population, the threat is not eliminated and populations can resurge dramatically. In all probability, the beekeeping community will have to deal with Varroa mites from now on.

Although chemical control has blunted the effects of the mites in individual bee colonies, it also allowed a myth to perpetuate itself. This is the belief that Varroa could be handled just like other problems in beekeeping by the individual beekeeper whenever and wherever it was deemed convenient and appropriate. The dynamics of Varroa-bee interactions, however, suggest something different.

It is now recognized that Varroa mites are not only a honey bee community problem, they are a beekeeper community problem. This idea was brought into focus by Marion Ellis, Nebraska State Apiarist at the American Beekeeping Federation meeting in Kansas City. In his presentation, he referred to an article in the December, 1991 issue of American Bee Journal entitled “How Varroa Mites Spread,” by Dr. Eva Rademacher (pp. 763-765).

Through a series of experiments, Dr. Rademacher found that Varroa mites rapidly spread among colonies in a beeyard. The main cause of growth of mite infestation is drifting parasitized bees, not natural increase of mites within individual colonies. The conclusion: It is not the infestation of a single colony, but rather the general rate of infestation for the entire yard that should be monitored.

Comparing two locations where infested apiaries were within two kilometers (1.2 miles), Dr. Rademacher also showed re- infestation rates to be dramatically different based on infestation rates of nearby apiaries. If the rate was 900 mites/colony or less (low invasion pressure), re-infestation in apiaries in close proximity was three times more than normally expected; if 900 mites/colony or more (high invasion pressure) were present, the figure rose to 11 times normal. Thus, according to Dr. Rademacher, “…it is not ‘hive mites’ which endanger the colony, but rather the ‘immigrants.'” Given this evidence, she suggests:

1. Nuclei or natural swarms which have been treated for Varroa, should be placed at locations where a low mite fluctuation from the surroundings (low invasion pressure) can be expected.

2. It is not helpful to treat just one or several of the colonies in a beeyard because of the danger presented by other infested colonies.

3. Beekeepers with beeyards rather close to each other should make arrangements to medicate their entire stock at the same time, because of the invasion pressure which leads to a rapid increase of mite population within only several weeks.

4. Invasion pressure also plays an important role when colonies are moved to other areas. Not only will a beekeeper want to determine the level of infestation in the new foraging area, but the keeper in that area should also be concerned about the level of infestation of incoming colonies.

5. Natural swarms should be medicated before being incorporated in the beeyard.

6. It is also important to prevent robbing. It has always been accepted that the robbed colony suffers. Now the robbing colony itself can be the victim from by invading mites.

The message is clear. Effective Varroa control should be undertaken as a beekeeper community effort. If not, then presence of nearby infested colonies (sometimes  called “Varroa bombs”) will quickly undermine the money and effort any beekeeper expends to control mite populations.

Perhaps the best example of communal Varroa control is found in the small country of Israel. Beekeeping there is highly regulated and strict penalties are in force for beekeepers that stray.  That country, as a consequence, has perhaps the best honey bee disease and pest control strategy in the world.