PARASITIC MITE SYNDROME (PMS) What We Know - Is Not Very Much For the past two to three years we have been seeing diseased bee larvae with symptoms resembling a cross between European foulbrood, sacbrood and sometimes American foulbrood. The Beltsville Bee Lab has found these diseased larvae to be infected with virus. The one thing that these samples of diseased larvae have in common is that they were all collected from colonies infested with varroa mites. The European literature is filled with reports of viruses infecting both brood and adult bees in close association with varroa mites. In addition, over the past several years many beekeepers have experienced bees disappearing in the early fall from previously healthy colonies. This situation is most likely associated with varroa mites, viruses or a combination of both. Symptoms Affected larvae die in the late larval or prepupal stage, stretched out in their cells with their heads raised. In the early stage of infection they are white but dull rather than glistening and look deflated. Later, the larva may have gray or brownish spots. Prepupa die after the cell has been capped and the cappings may be perforated or the cells may be uncapped completely by the bees. When the larval remains are stirred with a toothpick or small twig, they do not rope out but are globular (similar to EFB). Treatment If, as seems to be the case, the virus complex is associated with varroa mites, then controlling the mites is important to controlling or at least combating the virus. Because many of these infected colonies seem to collapse or the bees seem to ÒdisappearÓ in early fall it is necessary to control the mites well before this time. If used according to label direction, Apistan is effective in controlling varroa mites. Many beekeepers apply Apistan after the autumn honey harvest. However, we may need to consider treating colonies with Apistan in early spring (before the honey flow) or during the summer dearth (spring honey removed, fall honey supers not yet placed on colonies). By knocking down the population early, we may be able to protect the bees from mites and virus at this critical late summer/early autumn time, as well as through the winter. Please see ÒTreating VarroaÓ below for information on using Apistan strips. Although we do not understand why, treating varroa infested colonies with terramycin seems to help them survive and perform better. Also, nosema disease weakens the digestive tract of infected bees and may allow viruses and other pathogens to enter the honey bee's gut where they can do significant damage. Treating colonies in fall with Fumidil-B might also improve their chances of survival. For more information on treating honey bee colonies with terramycin or Fumidil - B, please contact me at the Department of Entomology.