A historical review of managed honey bee populations in Europe and the United States and the factors that may affect them.

The Western honey bee, Apis mellifera, is the most important animal pollinator in agriculture worldwide providing more than 90% of the commercial pollination services. Due to the development in agriculture the demands for honey bee pollination are steadily increasing stressing the pollination capacity of the global managed honey bee population. Hence, the long-term decline of managed honey bee hives in Europe and North-America is of great concern and stimulated intensive research into the possible factors presumably causing honey bee colony collapse. We here present a four-year study involving more than 1200 bee colonies from about 120 apiaries which were monitored for the entire study period. Bee samples were collected twice a year to analyze various pathogenic factors including the ectoparasitic mite Varroa destructor, fungi (Nosema spec., Ascosphaera apis), the bacterium Paenibacillus larvae, and several viruses. Data on environmental factors, beekeeping management practice, and pesticides were also collected. All data were statistically analyzed in respect to the overwintering mortality of the colonies. We can demonstrate for several factors that they are significantly related to the observed winter losses of the monitored honey bee colonies: (i) high varroa infestation level, (ii) infection with deformed wing virus (DWV) and acute bee paralysis virus (ABPV) in autumn, (iii) queen age, and (iv) weakness of the colonies in autumn. No effects could be observed for Nosema spec. or pesticides. The implications of these findings will be discussed.

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The German bee monitoring project: a long term study to understand periodically high winter losses of honey bee colonies

https://www2.hu-berlin.de/bienenkunde/Bilder-Downloads/Publikationen/2007/4-Nosema_2007_Klee_et_al_JIP_96_1-10.pdf

Widespread dispersal of the microsporidian Nosema ceranae, an emergent pathogen of the western honey bee, Apis mellifera

Nosema ceranae, a microsporidian formerly regarded as confined to its Asiatic host Apis cerana, has recently been shown to parasitise Apis mellifera and to have spread throughout most of the world in the past few years. Using a temporal sequence of N = 28 Nosema isolates from Finland from 1986–2006, we now find (i) that N. ceranae has been present in Europe since at least 1998 and (ii) that it has increased in frequency across this time period relative to Nosema apis, possibly leading to higher mean spore loads per bee. We then present results of a single laboratory infection experiment in which we directly compare the virulence of N. apis with N. ceranae. Though lacking replication, our results suggest (iii) that both parasites build up to equal numbers per bee by day 14 post infection but that (iv) N. ceranae induces significantly higher mortality relative to N. apis.

/pdf/nosema-ceranae-has-infected-apis-mellifera-in-europe-since-ag8o41ksy6.pdf

Nosema ceranae has infected Apis mellifera in Europe since at least 1998 and may be more virulent than Nosema apis

Nosema ceranae is a long-present and wide-spread microsporidian infection of the European honey bee (Apis mellifera) in the United States.

SummaryEstimates of levels of Nosema apis infection in honeybee colonies by three different sampling and examination combinations were correlated with honey yield. Samples of 60 bees were taken in early spring in Uppsala, Sweden, live bees being taken from the cluster and dead ones from the bottom board. Parallel samples of hive bees were examined individually and compositely. Dead bees were only examined compositely. The mean spore count/bee of each composite sample was estimated with a hemacytometer. The correlation of honey yield with Nosema level was much larger for samples of live bees irrespective of counting methods, than for composite samples of dead bees. The closest correlation with honey yield (-0·707) was found for number of honeybees infected. It is concluded that when colonies are being examined in spring to determine the effects of Nosema on honey yield, it is best to sample live bees and not dead ones and to examine the bees of the samples individually rather than compositely.

Egil Villumstad

Papers

Nosema Apis, Sampling Techniques and Honey Yield