I don't think anyone tries to falsely say DE works when there's no evidence, but I also think most of the time it does indeed not work.
My crazy theory—with nothing at all to back it up—is that there are some parasite populations it does work on. People have documented successful results. Then there are other populations (seems to be more common) that it does NOT work thickness of parasitic exoskeletons is variable and can be unintentionally selected to greater and more resistant thicknesses.
Yes makes sense. I've met people who say it works. Not for my mofos. On the permethrin starting today. Thanks for this. Interesting stuff. One study found thyme essential oil killed 45% so will use that but that does mean that will stop working eventually. Also ordered androlis predators for next week. No resistance to them but my ignorance has led me to spread them over a wide area while dismantling the coop so the androlis will probably only work at close range.