Diatomaceous earth doesn't help with much of anything. It's seriously dangerous to the lungs of all involved animals, including you, especially your birds, if it gets into the air. Large enough amounts to potentially harm invertebrates will risk getting it into the air and harming your birds. A bird with a mite infection should be given proper mite medications, not DE. It definitely won't help a fungal infection- it's just tiny bits of sharp dirt that scratch the exoskeletons of invertebrates. Fungi are not invertebrates.
Depends on how how you use it, it is food grade as recomended, I mix in 2 tbs into a very large food tub every once and a while, so it is not anymore dusty than regular feed. I am going to use it if I feel like using it, and I have only positive things to say about it. It is good for people to hear both sides though.

