Important study from an august research team sheds more light on the topic of brood mediated resistance and likely provides a more refined understanding of Suppressed Mite Reproduction (SMR):
  https://www.sciencedirect.com/science/article/pii/S0020751923000929?via%3Dihub

A few highlights:

The aim of this study was to gain a better understanding of the honey bee host mechanisms responsible for the SMR phenotype. This was approached by separating the adult bee behaviors from brood traits and measuring the rate of Varroa mite reproductive success. Adult bees were restricted from sections of brood on the same hive frame as brood that was exposed to adult bees. The hypothesis was that if mite reproductive success was reduced in the worker brood that was excluded from adult bees, then brood traits would be a significant contributor to the SMR expression in these populations, independent of the adult worker behaviors.

Mite reproductive success rates did not significantly differ between treatment groups of either caged brood or brood exposed to adult bees and their possible removal behaviors, irrespective of the population’s genetic background (χ2 = 2.45, degrees of freedom (df) = 1, P > 0.11). The only variable that did influence Varroa mite reproductive success was the population’s genetic background, irrespective of treatment (χ2 = 44.51, df = 3, P < 0.005). This study clearly distinguishes that adult bee behaviors are not involved in the expression of the SMR phenotype in these naturally adapted mite-resistant honey bee populations.

Although we hypothesise that the reduced reproduction of mites is influenced by brood factors in these populations, there could still be factors that we have not examined, such as hive environment, that could be influencing mite reproduction.


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