Colony losses, managed colony population decline, and Colony Collapse Disorder in the United States

Apis mellifera, CCD, Colony Collapse Disorder, Israeli acute paralysis virus, Nosema ceranae, pesticides, Varroa destructor, nutrition, stress Journal of Apicultural Research 49(1): 134-136 (2010) © IBRA 2010 DOI: 10.3896/IBRA.1. 49.1. 30 The beekeeping industry in the United States has faced a number of obstacles to healthy bee management in recent decades. These obstacles range from arthropod pests such as the tracheal mite (Acarapis woodi), Varroa destructor mites, and small hive beetles (Aethina tumida) to pathogenic diseases including RNA viruses and the microsporidian Nosema spp. According to the National Agricultural Statistics Service (2009), the number of managed honey bee colonies used for honey production in the U.S. has decreased steadily since the late 1940’s (Fig. 1). Even though it is clear that the number of managed colonies in the U.S. has declined over the last half century (Fig. 1), it has been difficult to determine actual yearly colony losses, since beekeepers in the U.S. routinely split (divide) their existing colonies every spring to recover losses they experienced the previous winter. According to vanEngelsdorp et al. (2008), surveyed beekeepers losing ~22% (95% CI: 15.9 – 27.5%) of their colonies during the 2007-8 winter, felt that this level of loss was “normal”. Despite the replacement of lost colonies through splitting, there was a net loss (-5.81%) in the total number of honey producing colonies from 2007 to 2008 (calculated from data provided by NASS, 2009), thus suggesting that “splitting” colonies is not sufficient to maintain the sustainability of beekeeping in the U.S. This probably has been exacerbated by the introduction of V. destructor into the U.S. Before its introduction, the total number of honey producing colonies in the U.S. decreased on average 0.06% ± 0.5 (mean ± s.e.) per year while the rate of decline increased to 1.5% ± 0.7 afterwards. Arguably, this decline reflects both the biological loss of existing colonies and the fact that some beekeepers chose to leave the industry in the face of extra expenses and the efforts needed to combat mite infestations, a trend documented in Europe (Potts et al., 2010). In fall of 2006, some beekeepers in the U.S. reported losing 30-90% of their colonies and the symptoms associated with the dead colonies did not match those produced by known bee pests / pathogens. Although annual losses above 30% are not uncommon for beekeepers in the U.S., the number of beekeepers reporting elevated losses appeared alarming as did the unique symptoms associated with the colony losses. Consequently, the apiculture community in the U.S. called the new phenomenon of elevated colony losses “Colony Collapse Disorder” or CCD. In an attempt to remove the ambiguity surrounding CCD, U.S. bee scientists defined some of the symptoms often associated with the phenomenon. In collapsed (dead) colonies, CCD may produce the following symptoms: 1. the complete absence of adult bees in colonies with few or no dead bees in / around colonies; 2. the presence of capped brood; and 3. the presence of food stores that are not robbed by other bees or typical colony pests. CCD symptoms often associated with collapsing (weakening) colonies may include: 1. an insufficient number of bees to maintain the amount of brood in the colony; 2. the workforce is composed largely of younger adult bees; 3. the queen is present; and 4. the cluster of bees is reluctant to consume food provided to them by the beekeeper. It has been difficult to assess the impact of CCD in the U.S. The Apiary Inspectors of America (AIA) and USDA-ARS estimate that honey bee colony losses for fall / winter 2006-7 and 2007-8 were 31% and 36% respectively (vanEngelsdorp et al., 2007; 2008). These loss estimates were based on telephone surveys of beekeepers, who managed between 10-18% of the 2.4 million colonies in the U.S. Nu-merous causes, including CCD, were reported as contributing to the colony losses during the 2006-7 and 2007-8 winters (vanEngelsdorp et al. 2008). The AIA and USDA-ARS conducted a similar survey for