You are on the right track to identify and treat the vegetation early in the growing season. One option in terms of identification is call the Illinois Department of Natural Resources fisheries biologist for your area, that is Fred Cronin (618)931-4217. He could identify the vegetation if you mailed him a sample. Collect a representative sample of the vegetation and place it in a plastic sealable bag, less the water, and send it to him. Aquatic herbicides are designed to control specific types of vegetation, so using the correct product is a critical step in the process.