Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Coontail elimination in 4 acre feet farm pond

Welcome to the forum. The downside to coontail is that it is resistant to herbicides and it's one of the harder plants to kill, so whatever you use will also kill any plants in the pond that are less susceptible to herbicides.

Since your pond is old, it has a lot of residual nutrients in it. Eliminating all the aquatic weeds in the pond will most likely create a large filamentous algae bloom.

Triploid Grass Carp are an option, but they probably won't do much this year. The recommended amount of TGC to stock is between 7 to 14 per surface acre of vegetation that you want controlled.

Sonar AS is actually cheaper per ounce of active ingredient. It doesn't really have a shelf life, so using part of a bottle will leave some for the subsequent years. I know some say 2 years but I have had it for 5 years and I see no degradation in effectiveness.

A rough way to calculate average water depth is take max depth and divide by 2. To get a rough idea of acre foot, take that sum and multiply it by the surface area of the pond. If your calculations are correct and you have 4 acre feet of water you will need 27 fl. oz of Sonar AS because you need a 90 Parts per Billion dosage over 30-45 days to kill coontail.

Sonar RTU has 3.79% Fluridone. Sonar AS has 41.7% Fluridone. Sonar AS is a one and done treatment (per year - you have a good seed bed in the bottom of the pond and no herbicide kills seeds). You will most likely have to treat every year for a number of years in a row to kill the plants that germinate from the seeds when using a fluridone product. You want to kill the plants this year before they set seeds. Coontail typically dies off during the winter here in the northern part of the USA and starts the next year from seeds. It will also propagate during the year from plant fragments.

When you look at the dosage rates for Sonar RTU, you have to use the rate for Watermeal to kill Coontail. Watermeal also needs the 90 PPB dosage. So the recommended Sonar RTU amount you will need to use for your pond is 6 quarts or 1.5 gallons.

Since your pond is only 0.5 acre, I would recommend using Diquat and Cutrine Plus liquid mixed together. Yes, it will take multiple applications. It is a contact herbicide, so you don't want to treat the whole pond at once, I would only treat 1/2 the pond at one time to prevent an O2 crash due to many of the plants dying at once.

It's not important that you reach the center of the pond, spraying out in a solid stream from the shoreline should work - you should be able to spray 20-25 feet out from shore. Endothall works good but it is toxic to fish if used incorrectly. You have to apply it from shoreline out so you don't trap fish up against the shoreline with nowhere to go. If using the Diquat mixture, I'd also mix in 1 fl. oz. of surfactant per tank mix - 15 fl ox. for your 15 gallon tank sprayer. I have a Cygnet distributor near me, so I use Cygnet Plus for a surfactant.

Oops, I almost forgot. Re: self harvesting. It is hard to tell because of the method of self harvesting. Since the plants grow from plant fragments, it all depends on how many fragments were generated. If many fragments, it could make the weed problem this year worse because of having more plants = more seeds to germinate this year.

If you are going to self harvest, I would use a net to minimize the amount of plant fragments, but as you found out it is very labor intensive. If you are going to use a herbicide, go buy a swimming pool thermometer. Start the treatments when the water temperature (not air temperature) is 60-65 degrees and climbing. That is when Coontail starts growing the fastest.