Had not seen this linked article before - another helpful addition! FYI, the tall grass in my upper yard bears itch mites starting in late spring/early summer which remain after grass is removed until winter frost. It causes ME problems, but have not noticed it being an issue for the chickens. I deliberately let it grow for the chickens to forage on the wild oats. I don't typically use the wild grass as bedding. It took me a long while to identify what was happening as the mites are microscopic. I end up doing yard work in these areas with a mixture of coconut and tea tree oil to discourage biting. Here are some additional links: "Is Your Hay Biting You?" the mysterious itch mite an organic spray treatment (never tried it)