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Economic and environmental significance of honey bees

 

Historically the importance of beekeeping has been underestimated in the agricultural economy. This has come about largely because the economic significance of this activity takes into account only the production of honey and other products of the apiary (wax, pollen, propolis, royal jelly, bee bread and venom).  Even so beekeeping remains an important source of income for small and middle-sized farms, and worldwide production of honey has been steadily increasing (Figure 1). United Kingdom (UK) production accounts for only 0.4% of world production, worth £10m-30m (http://www.defra.gov.uk/hort/Bees/index.htm) and £22m in 2006. This value may well be an underestimate since in the UK beekeepers are not subject to compulsory registration and their number is probably underestimated. However, honey bees also play a fundamental role in the pollination of cultivated and natural plants. In the UK alone, the annual value of the pollination of cultivated plants can be estimated as in the region of £120m  (Temple et al., 2001). In the wider ecology, the contribution of honey bees to the pollination of natural plants, which form the

base of the food chain, is priceless (Morse, 1997). Consequently, although beekeeping does not generally receive the public attention paid to other agricultural activities, honey bees are none-the-less central to agriculture and ecology and threats to their well-being should be taken seriously. For this reason honey bee diseases are included in the list of notifiable animal diseases of the World Organisation for Animal Health (OIE), but despite this listing we still know relatively little about many of the agents infecting honey

Tons x1000

Year

Fig 1.1: World honey production from 1998 to 2009 expressed in thousands of tonnes. The graph shows how, from 1961, the production of honey has been steadily increasing . This graph can be directly correlated with the increase in the honey bee populations. FAOSTAT data (http://faostat.fao.org/default.aspx).

bees, or about the interactions between microbes and honey bees in nature (Cordoni and Spagnuolo, 2007). This is particularly true of viruses with which this project is primarily concerned.

The attention of the media, in this area, has been focused on this area in the last few years because of a large-scale colony loss called Colony Collapse Disorder syndrome that will be described later in this thesis.

Although viral infections of the honey bee often result in covert infections, which rarely progress to overt disease at the colony level, they are still important because of their negative  effect on  the honey bee products (honey etc.)  and on the environmental impact due to the pollination service that the honey bees carry out.

In 1967 Bailey wrote “The sum of unseen losses in normal colonies may well exceed those in the very few colonies that became severely diseased, and virus-free colonies might be more vigorous...” (Bailey, 1967). This prediction has been confirmed later by mathematical models and by various authors (e.g. Martin, 2001). For example Ponten, and Ritter found that inoculation of honey bee pupae with Acute Bee Paralysis Virus (ABPV) can cause a reduction in the life span of the adults by 25% and result in reduction of the brood care by their nurse bees (Ponten and Ritter, 1992). Anderson and Gibbs found that Kashmir Bee Virus (KBV) can cause a reduction (as the diseased larvae are removed by the nurse bees) of the 16% of the larvae when they were fed with a solution containing the virus (Anderson and Gibbs, 1989). Even worse are the effects of Sacbrood Virus (SBV); Bailey found that feeding the honey bees with SBV contaminated pollen resulted in a reduction of the mean mortality rate (56 days (control) to 22 days) (Bailey, 1969). He also found that inoculation of newly emerged adults caused an earlier onset of the foraging period with the consequences of pollen foraging failure and an increased susceptibility to cold (Bailey and Fernando, 1972). Anderson found that SBV, given orally to larvae, resulted in an increase of the 21% of the larvae removed from the nurse bees (control 5%).

In conclusion, viruses of the honey bees could trigger colony death by weakening or even changing the behaviour of the bees in a specific evolutionary stage (e.g. larvae, pupae, nurse bees etc.), and as all the jobs are of vital importance in the hive, the colony will  struggle during the winter as the resources accumulated may be not sufficient.