This is at Lake Cherokee in Thomasville where my wife and I and a friend were walking this past weekend. They have a nice track that is 1 mile long I used to walk when I lived at the apartments next door. We sometimes look at weeds they have working to control. Here is one I have not seen at the lake before but can become an issue.
Water hyacinth is a floating pond weed that can get about 3 feet tall. It is also perennial. It has a purple/violet flower that comes up on a terminal spike. The roots are very fibrous underneath and develop into a thick mat resulting in oxygen depletions.
Many aquatic compounds have been successful at treating hyacinth like 2,4-D, diquat, and glyphosate. However, it is late in the season to think about treating. UGA Extension Aquaculture Specialist Dr. Gary Burtle says the only treatment option this late is diquat. It would be okay to apply a spot treatment with a 2% solution of diquat to the foliage to burn back plants. Then come back in March with another treatment to kill new growth.