I wonder out loud......
Taking off honey no doubt is a stressful event for the bees. Unless it was an uncanny coincidence of some other circumstance, it would seem that the SHB numbers increased dramatically about the time you took off the supers for extraction. So I wonder about the confirmed research that shows the alarm pheromone as a main attractant to a hive. This has been known to attract SHB from miles around. I never really thought about hives being targeted by SHB by such an event.
No doubt the dynamics of the hive changed when you took off honey. Were the bees reluctant to spend energy defending such comb? I say that because I have seen fully functioning hives (ferals) where at certain times of the year, they basically give up a portion of the comb and almost seemingly allow wax moths to take out a certain amount of comb. Was this along those lines, but the bees not able to deal with the more aggressive nature of the SHB, to which they really were only introduced to in recent times?
I would consider placing the super on end out in the open, and let the bees clean them off that way. The open nectar/honey smell, which actually may also draw SHB into your place would at least be away from your hive a bit. (not that the SHB would not find your hives anyways). But at least you can have the bees clean up the comb, keep the area they defend to a minimum, and you could freeze each super for a day or two, then seal in bags.
Certainly something needs to be changed. (although as with many things with bees, you may not see this scenario in another 20 years....or again, maybe next year will be the same) I would consider something to save the supers and comb, compared to crush and strain. With both options, you can lessen the comb area and limit the comb the bees need to defend. Not putting the supers back on wet may be the only thing you need to change.
How long did you have the supers off? And did you have SHB in the honey house or supers while you extracted? I have seen supers taken off of well defended hives, and within days of sitting in a honey house, develop SHB larvae in huge numbers. Although the larvae was not seen in the hives, they quickly took over the supers, both capped and uncapped. If this was allowed to happen (and the larvae at first are very small and easily missed in extracted supers) , then you placed them back on the hives, this would almost be a certain death wish as the bees could not deal with this advantage given to the SHB.
Certainly this should be a heads up and a red flag for those extracting in heavy SHB areas. Thank you Slickmick.