Title: Varying congruence of hygienic responses to Varroa destructor and freeze-killed brood among different types of honey bees Authors
Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 11, 2013
Publication Date: February 5, 2013
Citation: Danka, R.G., Harris, J.W., Villa, J.D., Dodds, G.E. 2013. Varying congruence of hygienic responses to Varroa destructor and freeze-killed brood among different types of honey bees. Apidologie. 44(1): DOI: 10.1007/s13592-013-0195-8 Interpretive Summary: Honey bees use a hygienic behavior to remove dead and diseased brood from sealed cells. Bees selected for fast hygienic response to freeze-killed brood (FKB hygienic bees, such as Minnesota hygienic stock) have good resistance to some diseases and moderate resistance to varroa mites. Bees with varroa sensitive hygiene (VSH bees) have been selected for response against varroa mites and have good resistance against this dangerous parasite. A simple, standard test can be used to measure the FKB hygienic response but measuring VSH behavior is much more technically difficult. It has been suggested that the ability of a colony to remove FKB and remove varroa mites may be highly related, so that FKB removal might be used as a simple way to select for enhanced VSH. We measured responses to both FKB and varroa mites in four types of bees that have had different selection histories. All four types removed large amounts of FKB but the removal of mites was much more variable. VSH bees effectively removed FKB and varroa mites, but FKB hygienic bees removed FKB at much greater frequencies than they removed mites. Control bees (with little selection for FKB hygiene) removed the least amount of FKB and almost no varroa mites. Outcrossed VSH bees (i.e., colonies from VSH queens mated to unselected drones) removed intermediate amounts of FKB and varroa mites. Overall, the results suggest that there is not necessarily a strong relationship between hygiene against FKB and hygiene against varroa. VSH bees appear to respond to varroa-related stimuli that are probably are in addition to stimuli that regulate a more generalized response of honey bees to dead brood.
Technical Abstract: Different types of honey bees, Apis mellifera L., have been selectively bred for enhanced hygiene (i.e., removal of affected brood from sealed cells) to improve resistance to diseases and parasites. Bees selected for removal of freeze-killed brood (FKB) have protection from several microbial diseases and have some resistance to Varroa destructor Anderson and Trueman. Bees with Varroa sensitive hygiene (VSH) have good resistance to V. destructor. We determined whether response to FKB would be a useful selection method for VSH. We measured the responses of both types of bees, plus F1 VSH bees and control bees, to combs with FKB and with infestations of V. destructor. All four bee types completely removed large amounts of FKB (77-88%) within 24 h. The removal of mites after one week was much more variable among bee types (VSH = 66%, F1 VSH = 51%, FKB hygienic = 14% and control = 3%). FKB cells were manipulated (i.e., had cell contents either completely or partially removed) more by VSH bees than by control bees; F1 VSH and FKB hygienic bees manipulated intermediate amounts of FKB. There was a significant relationship between 24-h manipulation of FKB and 1-wk removal of V. destructor but the relationship appears to have little practical relevance because of large inherent variation.