I am not sure that we are capable of stopping things from spreading, BUT, I do feel we can do some things to help slowing it down.
Like Ohiotuber said I think some who could have made a difference but was asleep at the wheel when things could have been done. When we opened trade with Russia and some of these other countries the ships came to our sea and great lakes ports full of ballast water from where they came.
Think huge aquarium, this gave us Zebra mussel's along with numerous other things that was present in the waters they came from. I do blame and feel like someone in our all knowing government should have seen this coming and had the ships flush there ballast before intering our waters. (Also all the oversea's shipping containers,with bugs and whatever)
I know most people will do the right thing and do what they can given information about what to do. When we look at all the ways things spead including by birds, wind, floods and so on it seems like a mission impossible thing, but I and many of you I know will fight it anyway.
I use a spray bottle of hull cleaner that I add bleach to, to clean my boat every time I take it out. As for the Zebra mussels you have to understand that they and there eggs can survive for 10 days to 2 weeks in or on your boat, even up in the engine water jacket. This we should keep in mind when we take our boats to places we may pick these up.
I do wish our states would post at ramps or access points what invasive things are in the waters we maybe using and how best to clean or prevent it from being spread. Most states are strapped for funds and may not be able to put in cleaning stations ( a good idea) but I feel they should at least be able to at least put up a sign advising us on the matter and what we can do to keep from speading
With places like FAOL and so many other places as well as the magazines we all get, I think word is getting out how serious and wide speard an issue this is for us all. As I said it only takes a few minites of time to do our part.
This is a different issue but I'll tell it anyway. Indiana spent over 5 million dollars draining and poisoning Boggs Creek lake a few years ago because someone released shad in it that ruined a great place to fish. 2 years after restocking and all they did to bring it back to being what it had been, someone had released shad back into the lake.(DUHH!!) The state has a several thousand dollar reward for information on who did it, I;d like to think they may find them, BUT I'd say they won't.

It's been said, your once a man and twice a child, and I've always said I wanted to live long enough to embarress my kids. I'm happy to report I'm well on the way to doing both..!! Jesse