Bees are subject to numerous pressures in the modern world. The abundance and diversity of flowers has declined, bees are chronically exposed to cocktails of agrochemicals, and they are simultaneously exposed to novel parasites accidentally spread by humans. Climate change is likely to exacerbate these problems in the future. Stressors do not act in isolation; for example pesticide exposure can impair both detoxification mechanisms and immune responses, rendering bees more susceptible to parasites. It seems certain that chronic exposure to multiple, interacting stressors is driving honey bee colony losses and declines of wild pollinators, but such interactions are not addressed by current regulatory procedures and studying these interactions experimentally poses a major challenge. In the meantime, taking steps to reduce stress on bees would seem prudent; incorporating flower-rich habitat into farmland, reducing pesticide use through adopting more sustainable farming methods, and enforcing effective quarantine measures on bee movements are all practical measures that should be adopted. Effective monitoring of wild pollinator populations is urgently needed to inform management strategies into the future.

https://science.sciencemag.org/content/sci/early/2015/02/25/science.1255957.full.pdf

Bee declines driven by combined stress from parasites, pesticides, and lack of flowers

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.

/pdf/the-german-bee-monitoring-project-a-long-term-study-to-3z4x4jb9ne.pdf

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

Emerging diseases are among the greatest threats to honey bees. Unfortunately, where and when an emerging disease will appear are almost impossible to predict. The arrival of the parasitic Varroa mite into the Hawaiian honey bee population allowed us to investigate changes in the prevalence, load, and strain diversity of honey bee viruses. The mite increased the prevalence of a single viral species, deformed wing virus (DWV), from ~10 to 100% within honey bee populations, which was accompanied by a millionfold increase in viral titer and a massive reduction in DWV diversity, leading to the predominance of a single DWV strain. Therefore, the global spread of Varroa has selected DWV variants that have emerged to allow it to become one of the most widely distributed and contagious insect viruses on the planet.

/pdf/global-honey-bee-viral-landscape-altered-by-a-parasitic-mite-15ju8w2tlr.pdf

Global Honey Bee Viral Landscape Altered by a Parasitic Mite

Deformed wing virus.

http://www.tsusinvasives.org/dotAsset/3b275f2a-205c-4012-b48a-038a13dddf8f.pdf

Biology and control of Varroa destructor

Deformed wing virus (DWV) normally causes covert infections but can have devastating effects on bees by inducing morphological deformity or even death when transmitted by the ectoparasitic mite Varroa destructor. In order to determine the role of V. destructor in the development of crippled wings, we analysed individual mites for the presence and replication of DWV. The results supported the correlation between viral replication in mites and morphologically deformed bees. Quantification of viral genome equivalents revealed that mites capable of inducing an overt DWV infection contained 1010–1012 genome equivalents per mite. In contrast, mites which could not induce crippled wings contained a maximum of only 108 viral genome equivalents per mite. We conclude that the development of crippled wings not only depends on DWV transmission by V. destructor but also on viral replication in V. destructor and on the DWV titre in the parasitizing mites.

Deformed wing virus: replication and viral load in mites (Varroa destructor)

Short Communication Deformed wing virus: replication and viral load in mites (Varroa destructor)

SUMMARY Although it has clearly been demonstrated in previous studies that
honeybees inspect their worker brood in a non-random fashion, it is still
unclear which signals and cues worker bees use to monitor the nutritional
state of their brood. Here we show that worker bees can recognize and quantify
the larval food present in a brood cell olfactorily and identify potential
mechanical signals produced by the brood. There is no evidence for additional
chemical hunger signals produced by the larvae. However, the pattern of
movement of larvae within their cells changes with their nutritional state and
might provide additional information to nurse bees.

/pdf/mechanisms-of-food-provisioning-of-honeybee-larvae-by-worker-21cc8pkgmk.pdf

Mechanisms of food provisioning of honeybee larvae by worker bees.

Simple Summary American Foulbrood is a bacterial disease of honey bee larvae caused by the spore-forming bacterium Paenibacillus larvae. It is a notifiable epizootic in most countries because it is highly contagious and lethal to affected colonies. For clinically diseased colonies, authorities often consider burning the only sustainable control measure, while infected but not yet diseased bee colonies can be cured by beekeeping measures. It is therefore of the utmost importance to identify such colonies. For the detection of P. larvae spores in infected colonies prior to the onset of clinical symptoms, different hive matrices can be used: brood comb honey, adult bees, seasonal hive debris, and winter hive debris. We evaluated the suitability of these matrices as sample materials for early P. larvae spore detection and demonstrate considerable differences in the growth of concomitant bacteria interfering with P. larvae detection and in the sensitivity and limit of detection of P. larvae spores. We conclude that brood comb honey and adult bees are equally well-suited as sample materials for the early detection of P. larvae spores, while hive debris samples should only be used when it is not possible to collect honey or adult bee samples from brood combs. Abstract American Foulbrood (AFB) of honey bees caused by the spore-forming bacterium Paenibacillus larvae is a notifiable epizootic in most countries. Authorities often consider a rigorous eradication policy the only sustainable control measure. However, early diagnosis of infected but not yet diseased colonies opens up the possibility of ridding these colonies of P. larvae spores by the shook swarm method, thus preventing colony destruction by AFB or official control orders. Therefore, surveillance of bee colonies for P. larvae infection followed by appropriate sanitary measures is a very important intervention to control AFB. For the detection of P. larvae spores in infected colonies, samples of brood comb honey, adult bees, or hive debris are commonly used. We here present our results from a comparative study on the suitability of these matrices in reliably and correctly detecting P. larvae spores contained in these matrices. Based on the sensitivity and limit of detection of P. larvae spores in samples from hive debris, adult bees, and brood comb honey, we conclude that the latter two are equally well-suited for AFB surveillance programs. Hive debris samples should only be used when it is not possible to collect honey or adult bee samples from brood combs.

https://www.mdpi.com/2306-7381/10/2/103/pdf?version=1675238187

Pia Aumeier

Papers

Biology and control of Varroa destructor

Deformed wing virus: replication and viral load in mites (Varroa destructor)

Short Communication Deformed wing virus: replication and viral load in mites (Varroa destructor)

Mechanisms of food provisioning of honeybee larvae by worker bees.

A Comparison of Different Matrices for the Laboratory Diagnosis of the Epizootic American Foulbrood of Honey Bees