Apidologie 34 (2003) 389-397
DOI: 10.1051/apido:2003032

Swarming in honey bees (Apis mellifera) and Varroa destructor population development in Sweden

Ingemar Fries^a, Henrik Hansen^b, Anton Imdorf^c and Peter Rosenkranz<sup>d

a</sup>  Department of Entomology, Swedish University of Agricultural Sciences, Box 7044, 750 07 Uppsala, Sweden
^b  Research Group Entomology, Danish Institute of Agricultural Sciences, Research Centre Flakkebjerg, 4200 Slagelse, Denmark
^c  Swiss Apicultural Institute FAM, Liebefeld, 3003 Bern, Switzerland
^d  State Institute of Apiculture, University of Hohenheim, 70593 Stuttgart, Germany

(Received 13 August 2002; revised 26 November 2002; accepted 11 January 2003)

Abstract
In a honey bee population of 150 colonies, the development of an introduced Varroa destructor mite population was monitored in swarming and non-swarming colonies for two years in a Nordic climate. The results demonstrated a reduced mite population as a result of swarming only for the first swarm season studied. In the second swarm season, there were much higher mite levels (based on debris counts of mites) and fewer colonies swarmed, but there was no significant difference in infestation levels of adult bees in the fall between swarming and non-swarming colonies. This result was interpreted as an effect of host-parasite interactions, where the detrimental influence from the infestation prohibited growth (and swarming) in some colonies, but allowed better mite reproduction opportunities (and swarming) in others. Surprisingly, the mite infestation levels of swarms in the late fall were not significantly different from those of swarming colonies the same year, indicating that swarm survival may be almost as much affected by V. destructor, as intact, swarming colonies. No horizontal mite transfer through robbing was observed. The results suggest that, horizontal mite transfer may not be as important in a Nordic climate where many bee colonies die over winter along with their mites, as it is in warmer climates.

Key words: Varroa destructor / Apis mellifera / swarming / survival / nordic climate / population dynamics

Correspondence and reprints: Ingemar Fries
    e-mail: ingemar.fries@entom.slu.se

© INRA, EDP Sciences, DIB, AGIB 2003