The new rules permit pesticides as a last resort to control invasive species like Eurasian milfoil, an aquatic plant sold for aquariums which is choking the bottom of marinas around the lake.
Several environmental groups and the agencies that provide drinking water from Lake Tahoe oppose pesticide use. They asked for a five year moratorium, but the state water board said no.
The pesticide regulations still must be approved by the Environmental Protection Agency.
