Here's another link about Milfoil from the State of Minnesota. It has a lot of research links. Lots of watershed groups and Universities will hold invasive species courses and workshops. If you're really concerened with them some of the workshops are really informative. I noted another poster mentioned another invasive plant on a watch/wanted list. People have to be careful where they dump their fishtanks out too. Besides cuttings on boats and trailers, sometimes the invasives in the right climates/conditions will take off from the tank wastes. I managed a couple of state parks years ago. One had about 577 acres of water that looks like it could be used as a monster/horror location it had/has the milfoil so bad. The state at one time used a aquatic weed harvester but that just made the problem worse as the fragments that cut loose planted elsewhere. Every year though I notice the problem of Milfoil getting worse up near the coves of Green's Basin. I sure wish they'd be a right fast way to getting rid of the stuff without ecologically harming the water, fish and animals.
http://www.fw.umn.edu/research/milfoil/milfoilbc.html