Hi all
One of the most widespread errors is that is necessary to use some form of Bond method (live and let die) to develop varroa resistant lines. True, that's nature's way but it is not the only way. Marla Spivak has long promoted hygienic behavior as a proxy with which bees can be bred to achieve better health. Unfortunately, new work shows this may not be the correct path:

[quoted for review purposes only]

> The removal of freeze-killed brood (FKB) has often been used as a proxy to assess the removal of Varroa-infested brood. The question is whether this approximation is reliable enough to estimate the benefits induced by the removal of Varroa-infested brood in unselected stocks. For this purpose, we investigated the relation between the removal of FKB and three other variables: (1) the percentage of pupae and workers infested by V. destructor; (2) the share of mites in brood compared to phoretic mites; and (3) the reproductive success of mites. 

> To be a reliable estimate, the removal of FKB should correlate with these three variables. Since hygienic behavior is naturally expressed and highly variable in unselected stocks, we chose to use such stocks to get a wide range of FKB removal. There was no correlation between FKB and the three other variables. We conclude that removal of FKB is not a good estimate for hygienic behavior towards Varroa mites in unselected stocks.

> In conclusion, the assessment of the hygienic behavior through FKB assays had previously been shown to be reliable to select for resistance against multiple brood diseases, such as American foulbrood and chalkbrood (Spivak & Reuter, 2001a Spivak, M., & Reuter, G.S. (2001a). Resistance to American foulbrood disease by honey bee colonies Apis mellifera bred for hygienic behavior. However ... we could not show any significant correlation of the outcome of the test with the infestation nor with the reproductive success of the mite.

Gil Leclercq, Tjeerd Blacquière, Nicolas Gengler & Frédéric Francis (2018) Hygienic removal of freeze-killed brood does not predict Varroa-resistance traits in unselected stocks, Journal of Apicultural Research, 57:2, 292-299, DOI: 10.1080/00218839.2018.1426350

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