I have done quite a few trap-outs and a couple of cut outs on Bees in Trees this year.
I have noticed the nest were infested with Small Hive Beetles and their Larva.
Last fall I was watching 5 bee trees going into winter, this spring I went to check on them and 4 out of the 5 was dead.
I watched 2 bee trees this season die.
Of the trap-outs I've did Hive Beetle Larva was very high.
Here is a picture of a tree when I took the trap-out down, notice the larva outside the tree.
When I took the plywood down the beetle larva was on the outside of the tree where the plywood was.
At another trap-out site I seen a mature hive beetle crawl out of the funnel, fly off and make a couple of circles and landed on the hive going straight for the entrance which was covered with bees.
The entrance was a 1 1/4 inch hole, the small hive beetle showed to be very aggressive showing no fear of the bees.