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Title: Repeatability of measurements of removal of mite-infested brood to assess Varroa Sensitive Hygiene

Author
item VILLA, JOSEPH
item DANKA, ROBERT
item HARRIS, JEFFREY - MISSISSIPPI STATE UNIVERSITY

Submitted to: Journal of Apicultural Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2017
Publication Date: 9/25/2017
Citation: Villa, J.D., Danka, R.G., Harris, J.W. 2017. Repeatability of measurements of removal of mite-infested brood to assess Varroa Sensitive Hygiene. Journal of Apicultural Research. 56(5):631-634. https://doi.org/10.1080/00218839.2017.1369707.
DOI: https://doi.org/10.1080/00218839.2017.1369707

Interpretive Summary: Parasitic mites originally from Asia (called Varroa destructor) debilitate and eventually kill colonies of honey bees. Most commercial beekeepers rely on chemical treatments to reduce the levels of mites. Honey bees with certain characteristics can maintain these levels low and eliminate or reduce the need for treatment. The characteristic called “Varroa Sensitive Hygiene” (VSH) makes adult workers more prone to find and remove cells with developing workers that are infested with the parasite. This characteristic is found at high levels in select colonies, but is not very common in unselected bees. We repeated one-week tests in colonies with VSH and in colonies from unselected sources by exposing combs with infested developing workers to the removal activities of colonies. Colonies with higher levels of the VSH characteristic responded more and the responses were more consistent. Unselected colonies had minimal responses but the measurements were more variable. These findings provide guidance to those wanting to select bees for this important characteristic. When the characteristic is at low levels in unselected populations, several tests of the same colony are recommended, and only colonies showing responses at the level of select VSH colonies should be used.

Technical Abstract: Varroa Sensitive Hygiene is a useful resistance trait that bee breeders could increase in different populations with cost-effective and reliable tests. We investigated the reliability of a one-week test estimating the changes in infestation of brood introduced into highly selected and unselected colonies. We repeated tests on the same 32 colonies up to five times and compared variation within colonies and between colonies of the two types. As expected, selected VSH colonies decreased infestation much more than unselected colonies (-77% vs. -5%, P<0.0001) and also produced final mite populations in the introduced comb with higher infertility (41% vs. 16%, P=0.002). The variance in percentage decrease in infestation of introduced brood within colonies was higher in the unselected group. These variances can be used to estimate the number of repeated tests required to detect true differences between colonies. In an already selected VSH population, potentially useful differences between colonies (ca. 45%) can be detected with only one measurement per colony. Multiple measurements of colonies (up to 5 replications) are required to detect similar differences between colonies in less selected and more variable populations.