[holding answer 10 June 2009]: Analysis of the results of this research within the Food and Environment Research Agency's National Bee Unit shows that the most important risk factor in the mortality or weakening of colonies is Deformed Wing Virus, a virus transmitted by the parasitic Varroa mite, clearly indicating failed or unsuccessful treatments of mite infestations.
This highlights the importance of improving standards of husbandry and is in agreement with results from earlier studies investigating abnormal colony losses in 2007. The impact of mite infestations was exacerbated by the unfavourable weather conditions over the last two years which did not allow colonies to prosper.
The weather conditions experienced so far in 2009 have led to far fewer losses. A final report with the results from the investigations into abnormal colony losses will be published later this year.