The only time I ever had to try DE for lice was then I got that first rooster who came to me covered in lice, like brown rice running all over his bum. This was the first year I had chickens and that's what I had in my arsenal at the time. He was all alone, in a metal dog cage with shavings in quarantine. When I found those things all over that poor boy, I removed all the shavings, dusted the heck out of him, got new bedding and dusted that. I think the reason it worked on him was because he was one bird in a metal cage in a tile shower in the basement bathroom, no transference to other birds or bedding or any crevices to hide in.
An entire flock with lice in a wooden coop? No way I'd ever depend on DE to kill all those lice in that situation. I cannot imagine how bad he must have felt, being malnourished, having lice and favus, poor guy. He was a different bird within a month and no hens ever had lice here. He was clean as a whistle when he went to live with them.
As far as worms, how the heck could it ever worm a chicken? It gets wet inside the bird. Plus, birds who have been necropsied and were on DE in their feed had dessicated intestines PLUS worms still. That was enough to tell me that it was not good to pour a bucket into the feed bag, certainly not at 2% or more of the feed! I use DE for what it's good for, but no more. It takes me two years or more to go through a 50# bag of it in the barn. It can be used sparingly to dry out under roost areas or in nests and such, but it obviously cannot be depended upon to kill almost microscopic mites or I would never have had to treat my flocks for them just recently. I am sure part of that is because of the old, arthritic hens who lay on the floor all the time and can't or won't dust bathe. My Zane was crippled and never had them, but he was in a separate cage, no shared bedding with anyone.
