I don't want to kill my worms either, and I have found that to be elusive information when using pesticides or similar products. I don't have many worms in my yard this year, but I don't use pesticides-only vary rarely and even then only on affected plants. We did have enormous amounts of rainfall this past spring and I wonder if that killed them out? I did find out that the slug killing pellets I use DO kill earthworms. So that may have something to do with it. I understood that to be a natural product, which of course does not mean safe for desireables. But since it does kill slugs and snails which are soft bodied I wondered one day about the worms and when I googled it, it does look like it kills. Not sure what to do about that, I have a slug/snail issue here pretty bad.
