Fluridone, Professional Application, and Patience

Fluridone is a specific chemical used to control a variety of aquatic plants in ponds and lakes. You may have seen it advertised as Sonar or Sonar Genesis. This is an effective tool and we recommend it in certain situations where we feel that it provides good value. It is not always the best approach, and determining whether it provides the best plan, as well as determining a professional application plan is our job as pond biologists and professional aquatic pesticide applicators.

Fluridone arrests the ability of a plant to produce chlorophyll and make food from photosynthesis. Chlorophyll is green and the absence of it will make the plants turn white. New plants may even appear from seed, and appear green. They will however turn white and die prior to them being able to mature and complete a second seeding cycle. This is likely very satisfying to observe only if you are a pond-nerd biologist.

Fluridone has several advantages and a few disadvantages:

Advantages

• Long lasting-assuming the herbicide is not flushed out. It should be active for several months without any boost applications.
• Controls many aquatic plant species.
• Long term protection against new infestations that can be brought in from birds, or wildlife.
• Controls species slowly over 30-60 days.* Good from a standpoint of protecting against an oxygen depletion due to rapid degradation of plant material.

Disadvantages

• Controls species slowly over 30-60 days.* Frustrating in that you have to wait for a longer period to enjoy a clear pond. This does need to be applied with a large dose of patience! And it is a good idea to set a date on your calendar 45 days from the date of application to avoid feeling impatient or temporarily disappointed.
• It will kill ornamental plants, like iris, along the pond bank. (NOT Cypress trees) It will also thoroughly kill all affected species, so there is not an option to affect duckweed and keep your water lilies.
• It does not control all aquatic plants; pennywort is one, and it may require an additional treatment with other herbicides. Some aquatic plant species have developed resistance.
• It is a more expensive treatment, so the plan should be a sound one.
• It does not degrade the plant material in the process of killing it, so additional applications of beneficial bacteria or enzymes may be necessary.
• It will not control algae, which may follow as other plants are treated and begin to degrade.
• It can be flushed out of a pond, requiring additional application.
• Eliminates the ability to irrigate from the pond/lake.

Fluridone treatments are applied in measurements of parts per billion. That is correct: nine zeros! The species, or group of species, after proper identification are used to determine the level of treatment which can vary by 900%. Proper identification, proper measurement of chemicals, and proper determination of the pond volume and the likelihood of flushing are crucial to a successful treatment. Also, the use of additives to speed penetration, increase effectiveness, and speed the degradation of dead plant material really help to increase the value of the application.

A professional biologist can determine if fluridone treatment is the correct plan for your pond, and ensure you get good value from the treatment by properly identifying nuisance plant species, making sound measurements, and prescribing a treatment plan, including additives and follow up monitoring.

Summer of 2019: A client had acquired a new property with a 20 acre lake. It was choked with several species of plants that made 90% of the water surface difficult to access, even with a kayak. Salvinia, Coontail, Yellow waterlily, Hydrilla, Primrose, Southern Naiad and a few others were present. 90 days after treatment, the lake is open and available for recreation.