AUGUSTA -- Voluntary boat inspections will again take place at boat ramps throughout Maine this summer, an effort to prevent invasive plants from spreading.

Once in a water body, milfoil and other invasive aquatic plants can degrade water quality, according to the Department of Environmental Protection.

Inspections of watercraft at boat ramps are aimed at intercepting invasive aquatic plants before they infest a lake or pond.

This year, additional inspection sites have been added on four lakes, bringing the total coverage to 79 lakes and one river.

Paul Gregory, an environmental specialist for the DEP invasive species program, said: "We are likely to exceed last year's record of 49,783 inspections which itself was a 23 percent gain over inspections conducted in 2006. Every boat inspection tallied represents one less opportunity for an invasive aquatic plant to infest Maine waters." No new invasive aquatic plant infestations were confirmed in 2007.

DEP provides $60,000 derived from a milfoil sticker fee to support organizations helping with the inspections. Most boat inspectors are volunteers. They only inspect with boater permission.

Gregory said 28 of Maine's 6,000 ponds and lakes contain an invasive plant species.

"While that proportion is the envy of more heavily-infested neighboring states and provinces, it also means we potentially have the most to lose," Gregory said in a news release. "Our courtesy boat inspectors provide a powerful line of defense."