|De Guzman, Lilia|
|KIRRANE, MARIA - University College Cork|
Submitted to: Journal of Apicultural Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2015
Publication Date: 2/4/2016
Citation: De Guzman, L.I., Rinderer, T.E., Frake, A.M., Kirrane, M. 2016. Brood removal influences fall of Varroa destructor (Mesostigmata: Varroidae) in honey bee (Hymenoptera: Apidae) colonies. Journal of Apicultural Research. 54(3):216-225. https://doi.org/10.1080/00218839.2015.1117294.
Interpretive Summary: The removal of Varroa- infested brood not only disrupts mite reproduction but also exposes the foundress mite and her progeny to bees’ aggression. Using brood deliberately infested with marked Varroa, we investigated the association between the removal of Varroa-infested brood and the removal of exposed foundress mites in Italian (IHB) and Russian honey bee (RHB) colonies. We found that RHB indiscriminately removed more Varroa-infested brood in a significantly lesser time than IHB colonies. At the end of the experiment, RHB colonies also had lower proportions of brood cells containing Varroa than IHB either in the Varroa-inoculated brood or in brood that were not inoculated with Varroa. We also documented that the more Varroa-infested brood removed, the more fallen mites collected from both stocks. Since RHB colonies showed strong and rapid hygienic responses to Varroa-infested brood and grooming responses to the exposed Varroa mites, these attributes probably are important components of this suite of factors responsible in suppressing Varroa population in RHB colonies. Since at least two IHB colonies showed high rates of brood and mite removal, these attributes can probably be improved through selective breeding in Italian honey bees.
Technical Abstract: The hygienic removal of brood infested with Varroa destructor by Apis mellifera disrupts the reproduction of the infesting mites and exposes the foundress mites to potential removal from the colony by grooming. Using brood deliberately infested with marked Varroa, we investigated the association between the removal of Varroa-infested brood and the removal of exposed foundress mites in Italian (IHB) and Russian honey bee (RHB) colonies. Our results showed that RHB colonies removed more Varroa-infested brood in a significantly lesser time (average = 87.9 ± 2.0% for 2.6 ± 0.1days) than IHB colonies (average = 61.9 ± 7.3% for 3.2 ± 0.1 days). For the inoculated brood that was not removed, RHB colonies had lower proportions of brood cells containing: a) live marked Varroa mites regardless of reproductive status (RHB =4.4 ± 1.3%; IHB = 17.7 ± 5.9%), b) dead marked mites (RHB = 1.1 ± 0.5%; IHB = 7.1 ± 2.2%), c) lost introduced marked Varroa mites (RHB = 6.6 ± 1.6%; IHB = 13.3 ± 2.8%), and d) reproductive marked Varroa mites (RHB = 8.3 ± 6.3%; IHB = 23.8 ± 6.9%) than IHB colonies did. These observations suggest that RHB colonies indiscriminately remove Varroa-infested brood regardless of mite status. Regarding trapped mites, the number of Varroa-infested brood removed positively correlated with the number mites that were trapped in both stocks. The majority of the trapped mites fell during the first three days post mite inoculation, which coincided with the highest rates of brood removal. The highest proportions of trapped gravid foundress mites were also recorded during this time, when host bees were on their early development. The comparatively strong and rapid hygienic response of RHB to Varroa-infested brood and the associated removal of infesting foundresses are likely parts of a suite of factors responsible for suppressing Varroa mite population in RHB colonies.