Hygienic behaviour selection via freeze-killed honey bee brood not associated with chalkbrood resistance in eastern Australia

Authors: GERDTS, JODY - La Trobe University; DEWAR, R. - Agri-Sciences Queensland; Simone-Finstrom, Michael; EDWARDS, TREVOR - Department Of Agriculture - Australia; ANGOVE, MICHAEL - La Trobe University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2018
Publication Date: 11/14/2018
Citation: Gerdts, J., Dewar, R.L., Simone-Finstrom, M., Edwards, T., Angove, M. 2018. Hygienic behaviour selection via freeze-killed honey bee brood not associated with chalkbrood resistance in eastern Australia. PLoS One. 13(11):1-13.
DOI: https://doi.org/10.371/journal.pone.0203969

Interpretive Summary: Since honey bee colonies in Australia are currently free from the varroa mite (Varroa destructor), research on how to reduce the impacts of infestations if Varroa does reach the continent are of importance. Such investigations include work on the behavioral resistance traits of honey bees. One such trait, hygienic behavior, is a behavioral defense of honey bees against various pathogens and parasites whereby adult honey bees are able to detect sick or parasitized larvae and pupae and remove them before they become infectious. A survey of hygienic behavior and brood diseases was conducted in eastern Australia to initiate a selective breeding program targeting disease resistance and provide a level of potential resistance to Varroa mites should they become established in Australia. The test population showed a remarkably high baseline level of hygienic behavior with 17% of colonies meeting or exceeding the established breeding selection thresholds. While environmental conditions, namely abundance of nectar, influenced the overall level of hygienic behavior of colonies, it did not influence the proportion of colonies deemed as either hygienic or non-hygienic. Surprisingly, hygienic behavior was not a significant predictor of the presence or intensity of infection of the honey bee brood disease chalkbrood. Given that hygienic behavior in other continents is known to be highly effective against colony-level chalkbrood infection, this study, along with reports from commercial beekeepers that chalkbrood infection is on the rise, warrants a deeper exploration of the host-pathogen relationship between honey bees and chalkbrood in Australia.

Technical Abstract: Hygienic behaviour is a social immune response in honey bees shown to help provide resistance to honey bee pests and diseases. A survey of hygienic behaviour and brood diseases was conducted on 649 colonies in eastern Australia to initiate a selective breeding program targeting disease resistance and provide a level of resistance to Varroa (Varroa destructor Anderson and Trueman and V. jacobsoni Oudemans) mites should they become established in Australia. The test population showed a remarkably high baseline level of hygienic behaviour with 17% of colonies meeting or exceeding breeding selection thresholds. Colonies belonging to a breeding program were 5.8 times more likely to be highly hygienic and colonies headed by queens raised from hygienic queen mothers were 2.2 times more likely. Nectar availability (nectar yielding flowering plants within honey bee forage range) influenced hygienic behaviour expression but was not a significant predictor of level of hygienic behaviour. Surprisingly, hygienic behaviour was not a significant predictor of the presence of infection of the honey bee brood disease chalkbrood (Ascosphaera apis) and was not influential in predicting severity of chalkbrood the infection in surveyed honey bee colonies. This study, along with reports from commercial beekeepers that chalkbrood infection is on the rise, warrants a deeper exploration of the host-pathogen relationship between Apis mellifera and Ascosphaera apis in Australia.