I would like to open up a new topic specifically dealing with SHB devastation on nucs. There are many fine articles and research publications all over the place that include chemical, mechanical, and other methods to control SHB infestation. (Note: I do not use the word to "eradicate," as that seems nigh impossible at this point) However, the proverbial wisdom of keeping strong colonies in the sun with a good measure of IPM does not seem to work well on nucs.
Nucs, given their small number and defenselessness, seem to attract SHB, often being wiped out, especially here in the south. Speaking anthropomorphically, nucs are analogous to children who have yet to develop immunization through "growing up" or getting shots
Those of you who raise nucs commercially in the south, what has been the most effective method keeping SHB's at bay? Yes, I've read numerous articles and viewed lots of videos on this topic, but I always come away with a feeling that these methods, while work to some degree, do not "hit the nail on the head."
Unlike mites, SHB's are new comers, having arrived in America only in 1992; as a result, bees have not yet had enough time to deal with this pest although there are some genetics that actively "guard" the beetles in their "jail" while at times, however inadvertently, feeding them, being fooled.
Strong nucs are okay with SHB, but if a queen doesn't mate or the nuc's bees age, the SHB grabs hold, we've found.
This sounds crazy but I'll use a propane torch to scorch out the inside of the nuc ( we use medium supers for our nucs with a wood bottom ) after removing the frames and bees as best I can. Then I vacuum out the residue with a small Dirt Devil cordless vacuum. When we restore the nuc we add a frame of emerging brood to repopulate it. This exercise can thwart the SHB sometimes.
The main defense against SHB in nucs is the condition of the colony: a queen-right and/or organized nuc, the SHB is kept in check. Queen-less or disorganized and the SHB gets ahead of the bees.