Varroa vigor linked to life cycle stage of the phoretic host
Dr. Zachary Huang (now at MSU) releases a research report on the phoretic host selection by Varroa. Varroa prefer nurse bees, and have better success on this age class.
One undiscussed implication of this research is the protocol step in sugar (and alchohol) sampling -- select sample bees from the brood frame -- is highly important. I have observed many otherwise responsible samplers take bees on a "grab and go" basis from anywhere in the hive.
A brood break would disrupt the demography of the hive and age the worker bee population, leading to a large reduction in Varroa fecundity.
The open access report is here:
A popular account is here: