As Michigan’s summer camping season gets underway, state officials are urging residents and visitors to avoid transporting untreated firewood to prevent the spread of invasive species that threaten the state’s agriculture and natural resources.

More than 140 pests and plant diseases can hitchhike in untreated firewood, traveling hundreds of miles before emerging to damage local ecosystems, according to the Michigan Departments of Agriculture and Rural Development and Natural Resources. Many of these harmful organisms, including hemlock woolly adelgid, Asian longhorned beetle and oak wilt, are difficult to see with the naked eye, making unintentional transport easy.