After drift from the herbicide dicamba harmed millions of acres of soybeans in 2017, environmental groups are worried that it could damage sensitive ecological areas, particularly habitats for monarch butterflies. “There’s too much that no one is watching,” said Kim Erndt-Pitcher, a habitat and agriculture programs specialist at Prairie Rivers Network, a nonprofit advocacy group for clean water in Illinois. Erndt-Pitcher said that as dicamba drifted and harmed an estimated 600,000 acres of soybeans in Illinois in 2017, it’s likely that much of the habitat for endangered species and monarch butterflies was also damaged. “With soybeans, people are out looking for it because it can affect their bottom line,” said Nathan Donley, a senior scientist at the Center for Biological Diversity. “With milkweed, the lack of complaints doesn’t mean it’s not there.