..., having done cut outs all these years I've never observed a preference for "open" bottomed cavities. I do see the advantage for mite drop, though, but I'd rather have bees that deal with mites more proactively than waiting on gravity.
Without gravity the mites would not fall...if they lost their grip on the bee they would still be in close proximity to the bee and probably reattach themselves. I tend to think that the bees have figured out the "pluck'em and let'em fall" technique and that this hygienic behavior of mite removal (and letting gravity help them) is about as proactive as they can get short of chewing up of the mites.
It would be interesting over a period of time for someone who does lots of removals to note the distance from bottom of the combs to the floor of the cavities along with noting the mite load of the colony.
It seems to me that solid bottom boards would recycle mites...mites fall to bottomboard, returning foragers enter, mites reattach to passing bees for a ride up into the combs. BUT...I'm a newbee will little practical experience just thinking out loud and I've seen experienced beeks state that they've seen no difference between solid and screened bottom boards.
The area I am interested in is how to trap them at a distance from the hive itself. We are already behind the eight ball if the hive is the bait. If we could ever find something like a japanese beetle trap that can be cheaply made in large numbers maybe we could saturate an area away from the apiary to intercept the SHB.
Wouldn't that be a wonderful sight to see, thousands of traps full of dead beetles.
From what I understand SHB are primarily nocturnal flyers (though I've seen them flying at sundown/dusk). What about 16-20 ounce drink and water bottles...free pickings everywhere....garbage cans, sports fields, side of the road, my front yard:whip:, etc.,. Three or four small slits tall and wide enough for the beetles to easily crawl through in the top "shoulder" area of the bottle. Maybe a dozen or so small holes (too small for the beetles to pass through) in the sides but towards the top for the aroma to escape from. The beetles like dark areas but being as they mostly travel when it's dark I wonder if the bottles being clear would matter....painting or covering them would make it hard to monitor the traps. Mix up your favorite bait and fill to just below the small holes in the sides. Place at different points to find the "honey holes".
I think that might work for something similar to the japanese beetle traps or to the weevil traps placed around fields. It would be cheap and easily deployed.
I wonder if a larger trap might be better. Something that could hold a couple of gallons of bait. Something that could give off a strong aroma like a rotting melons or what-have-you. A strong smell that would definitely float on the wind for a distance. Maybe a 5-gallon bucket for the trap? Use the same configuration of holes for the bucket as for the bottles? Larger "stuff" could be used in the bait compartment...chucks of watermelon, whole rotting bananas, etc.,.
Maybe use a combination of the bottles and buckets? Use the bottles to "fish" for those "honey holes" and place buckets at the most productive spots?
And, yes, David...great numbers of DEAD SHB would be a grande sight!
Anyhow, I was just thinking outside the box (maybe in a bottle?)...