# Help! Duck Weed



## I Fish (Sep 24, 2008)

Can someone please give me a hint on how to kill duck weed and water meal. We had an extension agent ID it for us, and we have followed the recommended removal, to the point of draining the pond, and leaving it dry for 18 months. Imagine the disappointment when it was back after 6 months of being refilled. The 1st time, it smothered the pond, and killed the fish. Now after restocking it, we're afraid of the same thing happening again. We really don't want to go to the expense of draining it again. Is there an effective way to at least control it, as it seems to be taking over again. If poosible, we would like to not harm the fish, as they've done great so far. Thanks in advance..............


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## [email protected] (Dec 22, 2006)

Who was the extension agent that told you to drain the pond to get rid of the duckweed and watermeal?

How big is the pond?

Hopefully Fishman will chime in a give you his expert opinion.


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## Big Joshy (Apr 26, 2004)

Im no expert but I belive expensive chemicals are the only way as far as I know. Sonar is one brand.
ive heard that duckweed seed can lie dorment on the bottom of a pond for many years and then grow when conditions are right so I think you were lead astray by draining it. Its also possible that you did eliminate it and some waterfoul brought it back to you. as fast as it can divide and spread anything is possible.


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## [email protected] (Dec 22, 2006)

OSU Extension recommends a mix of Cutrine Plus liquid and diquat
http://ohioline.osu.edu/a-fact/0014.html

Some grass carp may be able to keep it in check after it's killed off.

Tilapia would take care of it too but it's too late this year for them as well as an availablility issue.

Aeration would also help


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## Fishman (Apr 5, 2004)

Here's a thread about it from the past:

http://www.ohiogamefishing.com/community/showthread.php?t=98942

I've honestly never heard of draining a pond to get rid of it... pretty dog gone extreme... heck I guess ya could always fill it in to get of it though too 

The OSU recommendation of using Diquat (Reward) and Cutrine Plus could work under conditions where it was only in a confined area and not showing any signs spreading to the point where the pond becomes completely covered. 

I've see many ponds where it just lives in the first few inches of bank line and doesn't spread past that. I've hit it with diquat and other defoiliating herbacides and, yeah, I've killed it but it always comes back in a few weeks. If you miss one single plant it'll be back and it grows like wildfire. The only reason I can assume it stays confined in small areas is it maxes its self out on nutrient availabilty OR the nutrient availability is just on the threshhold of supporting the stuff and grows relativley slowly and the amur keep it in check. The biggest problem with amur is as they get bigger, and when they try to eat it it just passes through their gill rakers, unobstructed, back into the pond. Smaller herbavores can control the stuff easier since their rakers are closer together. Tilapia would in theory control this stuff pretty well! I've never seen it put into action but from what I understand pondfin is correct.

Seeing as your pond is still nutrient rich as it ever was, since it wasn't dredged when drained, Sonar is your best option. There's a very good likleyhood history will repeat itself again. Add an aeration system as well to help aid in the decomposition process of all the muck on the bottom and increase the O2 levels in the pond to help keep vegetation down some.

June/July is the best time to make applications since water inflow is at a minimum. You can certainly treat it in the fall, but I'de hold out till next year if you want to maximize your concentrations of flouridone, the good stuff in Sonar. Expect 365 day+ control and provided it's not reintroduced you'll be free of it.

Took this picture at a city park in NKY that we treated with Sonar for Duckweed that was for the most part 100% covered:










Note the cattails that look white on their lower halfs, that is flouridone poisoning inhibiting the plant from creating chlorophyll. Another close up shot of the cattails:










I know the cattails don't have anything to do with your duckweed/watermeal problems but I figured this was a good of chance as any to show you all the effects of Sonar.


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## I Fish (Sep 24, 2008)

It's a pond built in 1964, so we did "scoop" it out. Afriend of ours has one of those giant extending excavators, and it reached clear across the middle, with a very small (10' across) mound in the very middle. (That muck makes a great garden!) We used Sonar before we drained it, but it barely slowed it down. You mention Tilapia. Where is the best place to get them, and do they die off in the winter? Also, are pondfin a fish, and if so, where to get them as well? Thanks..............................


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## Big Joshy (Apr 26, 2004)

did you use enough sonar and did you give it enough time to work.


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## Fishman (Apr 5, 2004)

I hope I'm only misreading..... you used Sonar and you drained it. What kind of time frame are we talking?

If sonar didn't work within a month or two, you under applied it one of the most expensive mistakes you can make in lake managment, luckily the residual sticks around for a long time, so if you arn't starting to see results in a month you can add somemore and increase the ppms.

The guys have mentioned being able to get tilapias from local markets where they keep them alive. Jungle Jims down here in Cincinnati has them. They are temperature sensitive and will die every fall, BUT everything that I've read about them seems positive PLUS at the end of the year you get to have a fishin' derby and a fish fry  This is one reason I think people would probably have a difficult time adapting the the use of them because they'll have to smell or see a bunch of dead fish around the pond in the fall, but the die hards swear bye'em. They seem to be pretty inexpensive too, and depending on the vegetation situation can sometimes be stocked in low densitys.. I think pondfin knows the numbers.


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## I Fish (Sep 24, 2008)

We tried the Sonar 3 times. The 1st we followed the recomendations, the 2nd we used a little more, the 3rd was well above recomondations and probably excessive, but still it didn't work. That was three years ago, so I can't remember the amounts, just know it was expensive for what was accomplished. The fish kill happened prior to the first application. That was the motivation for it in the first place. We didn't dain the pond until the following spring, meaning the Sonar had about 10 months to work. I've been told it may have something to do with the depth of the pond. It was about 14' at the time. Do you know how much the tilapia will grow in a season? Thanks...........


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## Fishman (Apr 5, 2004)

Really don't know about tilapia growth rates, but I do know they grow extremely fast.

Deep water doesn't have any negative effect on Sonars function, only ones pocket book. Does your pond have heavy flow through? Water constantly leaving it basically?


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## [email protected] (Dec 22, 2006)

Here's the thread I started on tilapia. http://www.ohiogamefishing.com/community/showthread.php?t=94625

Tilapia typically reach market weight in 9 months in fish farming operations. In my pond they grew from 4-5" to 9-10" from Early May through the end of October. The first year I had them, I stocked 750 from 2" through 5", mostly little ones. It wasn't my intention to stock that many but I had an unexpected spawn in the grow out tank where they were spending the winter months. The second time I stocked them, I only stocked 2 males and 12 females in my 1/2 acre pond. They successfully spawned and kept the weeds under control. 10-15lbs of tilapia per acre is about right for maintaining a pond. You may have to double or triple that number if you have a lot of weeds. No matter how many I stocked, the most I found dead was about a dozen. Not a big deal at all since the weather was cool. Nature took care of them pretty quickly, I mulched a couple with the lawnmower too


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## fishmeister (Jul 29, 2004)

Do you have alot of runoff into your pond? High nitrogen levels from fertilizer (yard or field) or livestock will promote duckweed growth. They sequester nitrogen much more effectively than other plants, and therefore outgrow them. If you limit the nitrogen, you will limit the duckweed.


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## I Fish (Sep 24, 2008)

Yea, there is a little run off from our bird pens. We put in a diversion ditch a few years back, but still get a little. Will lime, or something help to nuetralize it?


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## Fishman (Apr 5, 2004)

I Fish said:


> Yea, there is a little run off from our bird pens. We put in a diversion ditch a few years back, but still get a little.



good god man! I'de correct that issue asap before going any futher.


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## 3xHebb (Nov 10, 2007)

A few pond owners i know around my area use barley straw take care of weed problems.My wifes aunt has a 2 acre pond and they used a few burlap sacks filled with barley straw and tied them off with a milk jug in a few weeks the pond was clean.


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## Fishman (Apr 5, 2004)

Unfourtantley barley straw won't do anything to plants, only algae.


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