Lake Advice Lake Weed Control
The numbers of emails I get about lake weed control tell me that it is a major issue right now. One in particular came from a past client, and the timeliness of the situation struck me as appropriate. I decided to include it and my response here, and if you have lake weed problems, it will be of interest to you. The names and other identifying features have been removed:
The email:
"You treated our lake for us two or three years ago and did a good job. You also said that the chemicals wouldn't do a lasting job with our clear water and that we needed to increase nutrients to cause an algal bloom that would shade out aquatic vegetation -- primarily coon tail, I think. You were certainly right as we now have one of the most impressive coon tail accumulations in the U.S. As you will recall, the lake is about 25 acres with much of it quite shallow. Can you think about this problem a bit and give me a rough ballpark figure on what it might cost to treat the water chemically and then to follow up with a fertilization program that would give us a healthier and more pleasing lake? Many thanks." (Name withheld)
My response:
I am sorry that I could not get back to you in a more timely way, and I am also sorry to hear that your problems with the lake continue. It is an unfortunate thing, but sadly, it is the nature of things. If memory serves me correctly, I treated about 10 acres around the edge of the lake with a mix of liquid Copper, and Diquat, and that is what I recommend again. It is the best combination outside of the more expensive granular products. This is the process I would follow:
- In the situation you describe, the weeds should be treated with a half and half mix of Copper liquid and Diquat, at at least 1 gallon each per acre. In this case, if the infestation is as bad as it sounds, you might want to raise that figure to 2 gallon each per acre.
- The chemical should be given enough time to kill the vegetation, and to tell if the job was complete. Often, if the vegetation is very dense, a second application may be needed. If this is the case, the second application should be made, and then allowed to work until the plants sink.
- I would check the pH. It should be around 8.6, and no lower than 6.8. If it is lower than 6.8, the lake should be limed.
- Check the water clarity with a secchi disk. If it can be seen in the water at a depth of 24 inches or more, the lake should be fertilized to produce algae bloom.
- Fertilizer, preferably 0-20-5, should be applied at a rate of 40 lbs. per acre. The calculations are based on the amount of phosphorous, so a 0-10-0 application would be 80 lbs. per acre, and a 0-40-10 would be 10 lbs. per acre.
- Fertilization should be continued in 2 to 3 week intervals until October to gain, and maintain the bloom. If the water begins to get too green, fertilization should be stopped until it clears a bit. 18 to 24 inches is the perfect secchi depth. 12 or less inches means too much algae, and too much fertility. Back off until the water clears to about 18 or 20 inches. This should be started as soon as possible.
This should produce the plankton needed to color the water, prevent excessive weed growth, and make your fish a lot fatter and happier!
I have just about ceased doing aquatic applications. Other work has filled the gap, and there are just too many pitfalls to the aquatic work. I have had a small number of cases where folks did not want to pay to have the follow up work done, and did not do the follow up themselves, causing a bit of ill will when the weeds returned. That added to the poor state of the economy, and the rising cost of the materials with which I work, have made it difficult for me to justify continuing. I do a limited amount of pond work close to home, with folks that know the ups and downs of the process, and I also do some paid consultations.
The End
I left that last part in to make the point that if you do not do the follow up, you will have the problem return. Please look through our lake management section for other related information, and other more severe options.
