Mathenious from Lorman writes
What is the application to kill coontail moss and how long does it take to start seeing results?
Rodeo Herbicide is not labeled to control coontail/hornwort or any other submerged weeds. You will need to use a different active ingredient, such as Diquat, fluridone, or flumioxazin for best results. Diquat is a contact kill herbicide that works very quickly, but you may need to apply more than once, depending on how good the coverage is with your first application. Fluridone is in Sonar products, which are systemic, so they move more slowly, but work to kill the plant completely. This article from TAMU Aquaplant has more details on treatment recommendations for this weed.
Answer last updated on: 04/09/2018