The Scottish Honey Bee Health Surveys 2012 and 2013 analyzed the importance of bacterial diseases and other potential factors impacting bee health. Their conclusion: “A significant percentage of annual honey bee losses can be attributed to the direct effect of cold weather and to the indirect effects of summer weather on colony strength and mating.” Pesticides were not identified as a cause of colony loss.
In apiaries in which Varroa mite was present, winter colony losses increased with the severity of the mite infestation, says the study. The risk of overwintering losses increased even more, if a colony was already affected by nutritional stress or diseases such as Nosema.
The authors’ findings are, however, accompanied by an upbeat message: “Many of these risk factors can be mitigated by introducing effective disease control and establishing better husbandry practices to alleviate the effects of the increasingly unpredictable Scottish weather.”
Here the link to the 2012 results – the 2013 results will be published later this year.