All of them attack nothing but their host purple loosestrife, Blossey said. The watermilfoil is but one weed in thousands. In New York, for example, there are more than 1,400 non-native plants grown. Blossey said that recreational lake users may be inadvertently contributing to the problem. For example, as small boat motors run across the lake, the propellers could churn the milfoil, allowing it to take root elsewhere in the lake, and boaters could easily transfer it to other water bodies inadvertently.
Scientists cringe at the thought of using chemical herbicides on such underwater weeds.
And chemicals provide only varying degrees of success. Biological control seems to be the most appealing method of tackling the problem. The search for biological control continues. Nor have those methods always been well-endorsed or financially supported.