I think there is too much moisture in the screen bottom. The hive is sitting up +/-8" off the ground on cinder blocks with the holes horizontal. It only get about 5 hours of good sun. The screen bottom is about 4" deep, has a access door on the back and at this time I keep a tray in the bottom with DE in it. The screen bottom has a slatted rack on it and then the brood box. Their entrance is reduced to 2", new package this year. I clean the tray once a week but have noticed a lot of mold in the tray recently and on the bottom. I looked in this afternoon and the sides have mold on them, sorta a light gray, and the wood, unpainted, is very damp. The present thought is to move the hive forward about 6 feet for better sunlight as well as put it on a new slatted rack and screened bottom board and trim some of the lower hanging limbs which have already been trimmed to 15'-18'. I think this is going to be a challenge because a lot of bees tend to hang out on the front porch as well as in the slotted rack. Thought was to do it just before it gets dark and set the existing bottom against the new one and let them move in. I would be moving the brood and super box.
There is a lot of fanning going on. They are even fanning the crack between the entrance reduce and the brood box. They are doing well, just added a super May 1st.
before going through all that trouble open the entrance up to 6" or 8" and see what happens.
if they are storing and curing nectar it releases a lot of moisture and it's hard to ventilate the hive with a 2" opening.
If it doesn't completely solve the moisture issue it will help enormously.
some use a top entrance as well as a bottom entrance that helps with ventilation/air flow in the hive.
(some other ways beekeepers increase hive ventilation: a notched inner cover, a 3/4" hole drilled in the face of the top super, setting the lid on nickles (5 cent coins) placed on the two front corners of the top hive box that raises the outer cover a bit for air flow, some set a super back a bit from the one below it to create a bee opening.)
Cut me new strip and put it in place. Still lots of fanning but at least they have room now. I'll limb up those trees tomorrow or Sunday. I put a top entrance in one of my hives last year and that is all the bees use. The bottom is still there, 1" opening, and I have seen the fanning from time to time. Haven't quite figured out the robbing prevention with a top entrance.
While I'm at it I'll make some more entrance reduces with 7" openings for the other hives, I split the difference. Might end up with top entrances on all of them.