In parallel to reports of dramatic colony losses of up to 35% in the US, Israeli commercial beekeepers have estimated an annual loss of 25%. Moreover, their colonies have not been as strong as previous years and honey crop yield has been reduced. From 58 beekeepers (46 000 colonies) interviewed, 40% complained of extensive colony loses during 2008.

Aiming to find the possible causes for the decline of local colonies, a comprehensive study of the incidence and characteristics of colony losses in Israel was initiated. Our goals were to evaluate (a) the extent and symptoms of colony decline and losses, country wide; and (b) the role of pathogens and parasites on colony health.   

An elevated incidence of high losses was more common in rather small beekeeping operations (less than 100 hives). professional management might have played a significant role in prevention of losses, since the lowest losses were reported by growers implementing prophylactic treatments against Nosema and Varroa. 

During the winter of 2008–2009,  colony population was, overall, normal and bees with disease symptoms (sacbrood, paralysis or deformed wings) were rarely observed (9%). However, PCR examination revealed that 73% of the tested hives displayed asymptomatic virus infections (BQCV, IAPV, DWV, VaDV-1, SBV, ABPV).  

In 42% of them, more than one virus was detected in the same sample. Some colonies were infested with Nosema or Varroa as well. Only 5% of the hives in the survey were diagnosed as free of pathogens. In summary, we found that a high proportion of apparently healthy colonies bore multiple pathogens. 

Evaluation of colony losses in Israel in relation to the incidence of pathogens and pests, Apidologie

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