MINNEAPOLIS, MN (AP)-- An aquatic weed that grows really fast and is really, really hard to kill is creeping across the Great Lakes region.

Starry stonewort forms dense mats in lakes. It first turned up in North America in 1978 in the St. Lawrence River in New York state. Researchers think it probably arrived in ballast water from ships entering the Great Lakes.

It wasn't a big concern for about 30 years. Then it took off. Now it's widespread on Michigan's Lower Peninsula, where it has infested more than 200 inland lakes, and parts of western New York.