Fasting and dancing until the vision is altered and the body weak -- that's a ceremony. But when 27 Native American dancers at last month's Gibson Sun Dance in Idaho fell ill with vomiting, lung disorders and blackouts, tribal leaders ended the three-day rite early. Health officials say the illnesses are a mystery, but members of the Shoshone-Bannock tribe, who hosted the festival, blame pesticides sprayed on reservation land leased to local farmers. Now the Shoshone-Bannock are calling for a ban on pesticides on all U.S. reservations. "We should be role models in keeping the earth clean," says sun-dance chief Robert (Dude) Perry. "We have to start practicing what we preach."