I recently ran across a publication of results from an interesting study by a number of honey bee researchers including: Dennis vanEnglesdorp, University of Maryland; David R. Tarpy, North Carolina State University; Eugene J. Lengerich, Pennsylvania State University; and Jeffery S. Pettis, USDA-ARS Bee Research Laboratory. The study involved tracking 80 hives of honey bees in three different migratory beekeeping operations, as the hives traveled up and down the east coast of the United States providing pollination services. The purpose of the study was to asset the hives for various health and colony risk factors which may impact the health of bees in the hives and contribute to colony loss of the hives and to attempt to determine which of these may be associated with the death of the bees in the hives (colony loss). Testing for these stress factors was continued through the life of the study, a ten month period from March 2008 through January 2009. Monitoring, including both visual periodic observations (made during hive inspections) and testing, included American foulbrood, European foulbrood, chalkbrood, sacbrood, deformed wing virus, queen events (including queen loss or supersedure), brood pattern quality (poor being more than 20% open cells), and varroa mite and nosema spore load. Another newly named disease, Idiopathic Brood Disease Syndrome (IBDS), was also monitored. IBDS is described as a disease characterized by dead honey bee brood that appear melted down into the bottom of the cell. This dead brood is similar to what has been in the past described as symptoms of Parasitic Mite Syndrome (PMS) and in appearance to scale (dead brood) found in brood killed by American Foulbrood or sacbrood, but called here IBDS, due to the opinion of the authors that it is not caused by varroa mite infestations, but from an unknown cause.
By the end of the ten month study, 62 of the 80 colonies (56%) had died. Most associated factors associated with this colony loss included queen events and colonies diagnosed with IBDS. Colonies where either of these factors was observed during a hive inspection, were three times more likely to be dead by the next inspection (conducted about 50 days apart). Increased prevalence of sacbrood virus was also found in colonies that did not survive. You may access the results of this study: Idiopathic brood disease syndrome and queen events as precursors of colony mortality in migratory beekeeping operations in the eastern United States, as well as a press release from North Carolina State University, which first drew my attention to the study. I encourage you to read both the press release and the published results of the study.