The Ivermectin or the DE?How do you apply it?
Ivermectin 5% Pour-On for Cattle is two drops on the back of the neck with an eyedropper. Part the feathers to get it on their skin. Best done at night when they're perched. This was for silkies. If larger birds, I'd go three drops. Repeat in 10 days.
DE: Kick the chickens out of the coop. Put on a mask. Grab a handful and sprinkle everywhere. All over the floor, in the nests, and on the roosts. I sprinkle it all around the outside of the coop too, and in any dustbaths they've made in the gardens. Also around the house to kill ants or whatever else.