I'm not sure the Fluridone will work fast enough to kill the CLPW before it produces turions and seeds in your pond. IMO you are rather late in the season for your attempt to kill your CLPW. Ideally the CLPW should be treated as soon as the pond water is 55F when CLPW starts growing fast. . Because you are in north Montana and CLPW matures later in the year compared to more southern states the Furidone might stop the current CLPW growth infestation before it makes the dormant or winter buds called turions and also the annual seeds. Check numerous near surface plants in 2 to 6 ft deep to see if turions have formed in the places were many of the leaves join the stem. See a large turion in this link - Turions are not always this large, some are smaller and still capable of making new plants
https://extension.umn.edu/identify-invasive-species/curly-leaf-pondweedhttps://www.montana.edu/extension/i...sion_publications/Curlyleaf_pondweed.pdfIf your plants have turions then IMO it is almost fruitless to spend money killing the CLPW now because the chemical will NOT kill the turions. Turions sprout in early Fall or Spring and can lay dormant and sprout in 1-2 maybe 3 years later. CLPW is a pest and truly an invasive persistent species. Wait and use Fluridone in Fall or early spring 2025.
What I have done in your current time limited situation is do a fast kill with diquat either Reward or Harvester or similar brand name. Be sure to use the one with strong active ingredient of 37.3%. Montana Extension suggests to use diquat early in the season before other good submerged pond plants are actively growing. this means an early Spring treatment water around 55F-60F.
Diquat works best when water clear and often does not do a real good kill if the water is murky and silty. Diquat will kill most all submerged leafy plants, HOWEVER it will NOT kill Chara since as esshup says it is a higher form of problematic algae difficult to kill. . Read the label for proper usage. For ponds with depth esp 10-14ft I ALWAYS inject the chemical dosage into the deep pond layer to make sure all the CLPW absorbs the chemical for a good kill. I also inject deep the Fluridone when I use it in the Spring treatment. If you apply the diquat properly at the right concentration the CLPW should be turning brown and dying in 5-10 days.
Once you get the CLPW killed back, I always use Fluridone in the fall and/or early spring for another long term kill time as the old dormant, resident turions and seeds sprout during the next 2-3 years. You will fight CLPW for several years or longer due to late sprouting turions and sheltered plants that do not get killed with each herbicide treatment either with diquat or Floridone. Floridone is actually best to use because it is active and kills a long time for each treatment working on dormant turions as they sprout. Low dosage (10-12ppb) or concentration of Furidone often does not kill other beneficial pond plants. When you use the low Fluridone dosage it is best to apply a 2nd bump or refresher (5ppm) dosage 10-20 days after the first application.
