> Whatever the precise mechanism, it now seems clear that when honeybee colonies are forced to live in identical hives that are clustered in an apiary, a high level of drifting can occur and colonies can be vulnerable to V. destructor and the viruses that the mites carry, especially if one or more of the clustered colonies collapses. Seeley, Thomas D., and Michael L. Smith. "Crowding honeybee colonies in apiaries can increase their vulnerability to the deadly ectoparasite Varroa destructor." Apidologie: 1-12.

See also: 

"Autumn Invasion Rates of Varroa destructor (Mesostigmata: Varroidae) Into Honey Bee (Hymenoptera: Apidae) Colonies and the Resulting Increase in Mite Populations"
Journal of Economic Entomology 107(2):508-515. 2014 
Eva Frey and Peter Rozenkrans.
Apicultural State Institute, University of Hohenheim, D-70593 Stuttgart, Germany
Corresponding author, e-mail: [log in to unmask]
doi: http://dx.doi.org/10.1603/EC13381 

ABSTRACT 

The honey bee parasite Varroa destructor Anderson & Trueman can disperse and invade honey bee colonies by attaching to “drifting” and “robbing” honey bees that move into nonnatal colonies. We quantified the weekly invasion rates and the subsequent mite population growth from the end of July to November 2011 in 28 honey bee colonies kept in two apiaries that had high (HBD) and low (LBD) densities of neighboring colonies. At each apiary, half (seven) of the colonies were continuously treated with acaricides to kill all Varroa mites and thereby determine the invasion rates. The other group of colonies was only treated before the beginning of the experiment and then left untreated to record Varroa population growth until a final treatment in November. The numbers of bees and brood cells of all colonies were estimated according to the Liebefeld evaluation method. The invasion rates varied among individual colonies but revealed highly significant differences between the study sites. The average invasion rate per colony over the entire 3.5-mo period ranged from 266 to 1,171 mites at the HBD site compared with only 72 to 248 mites at the LBD apiary. In the untreated colonies, the Varroa population reached an average final infestation in November of 2,082 mites per colony (HBD) and 340 mites per colony (LBD). All colonies survived the winter; however, the higher infested colonies lost about three times more bees compared with the lower infested colonies. Therefore, mite invasion and late-year population growth must be considered more carefully for future treatment concepts in temperate regions.

Kind regards,

Ghislain De Roeck,
Belgium

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html