15 to 50 mites a day after treatment is almost no mites. But they might be cleaning out mite infested brood. They might also be getting rid of drone brood that they don't think they need anymore. I don't think the oxalic will kill pupae. Pupae are sealed in cells. I haven't even noticed open brood dying let alone pupae.
Your honey flow might be over for now and like MB said they are starting to cut back on brood. This is a normal cycle in beekeeping. Yes it is alarming but the bees know what is going on and how to keep the hive healthy.
as theyve said there are lots of reasons for the dead brood so dont get too concerned.
ive never had any luck figuring out what is happening looking thru the pile of dead at the entrance. however, you can get some ideas if you look at a frame of capped worker brood. this time of year, super hygenic bees that have mites will have cells uncapped and brood being torn out in various stages. look for the opened cells and chewed up pupae. also if youve got a screened bottom of some type, now is the perfect time to find destroyed mites from aggressive grooming behavior. looked for the amputated legs and crushed shells.
The removal of brood seems to have stopped.
Thanks for all the advice.
I am feeing 2:1 syrup right now and trying to leave them alone as much as possible. I will treat again with Oxalic in October and see if there is the pattern of brood removal again. I'll report back either way.