Re: Resistance to varroa : what mechanisms?
I am seeing evidence of accumulation of multiple small genetic effects that result in gradually increasing mite tolerance. This is accompanied by ongoing attrition as susceptible stocks are wiped out year after year. The way to keep this going is to produce large numbers of colonies, let mites destroy the susceptible as fast as possible, and breed from the resistant colonies. Guess what treating for mites prevents?
IMO, it would be counterproductive to focus entirely on one trait such as VSH when other traits such as mite entombment are available and effective. We should be working on bees that combine as many resistance traits as possible, caveat that some may be mutually exclusive.
NW Alabama, 46 years, 24 colonies and growing, sideliner, treatment free since 2005, 14 frame square Dadant broodnest