Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Duckweed control?

MY FELLOW AMERICANS!Let me make this perfectly clear: I am not an actor. Or a politician. But I did stay at a Holiday Inn Express last night. We have beat this dead horse til it is even unacceptable to the fast food industry. So at the risk of being run out of office I would like to start this topic over at the top of the page. The topic I am speaking of is aquatic chemical safety. I am inviting all professional aquatic applicators & "Common Citizens" to weigh in with their own words on all chemicals-one by one-starting with Sonar. You guys write the posts & I'll pour the drinks. See you all at the bar upstairs. DOC

Doc: I'll vote for that! Thanks for the humor. Have a great Easter. KD

Lakedoctor-no I didn't have any training prior to using the chemical. Hiring a professional is always the best option. I was just trying a small area to see how well this stuff worked. I think the name of it was Aquathol granular. Anyway, it scared me, I will be much more careful in the future.

David,
Just for your info, they have changed the formulation of Aquathol Granular to a heavier and more concentrated product called Super K. I remember the dust from the Aquathol flakes and was cringing when I read your post. I think that you may have reminded some of us to be more careful with our PPE's.
Robert

I have a small pond (about 85' x 45'). I want to use Reward. I plan to use a pump sprayer.
How much Reward per gallon of water?
How much nonionic surfactant per gallon of water?
What can I use for nonionic surfactant?
The Duck weed is not bad yet, but I need to get on it fast.

I get good results with one gallon per acre Reward on duckweed but two gallons per acre is not an uncommon application rate. It depends on the water chemistry and turbidity. Diquat is toxic to fish in soft water at 245 ppm. If your pond is 3 feet deep on average putting 2 gallons of Reward into your pond would be about 1ppm active diquat. Thats with mixing it very well, in reality most of the diquat will be bound by dirt particles. So you see it would take quite a lot of Reward to kill fish with diquat. (about 400 gallons in a pond your size if my quick figures are right)

When treating duckweed with Reward think of it like mowing the yard. One or two times per year wont look very good. keep an eye on the duck weed and treat accordingly. Dont let it cover the pond or you will be asking for oxygen problems after the treatment. As long as its not covering more than 20 % of the ponds surface you can spray weekly. If you get a thick infestation you will need to wait several weeks between treatments. allowing the weeds to fully rot away before spraying again.

with such a small pond you may consider an aerator to help with oxygen

You could probably get away with one pint to one quart Reward per gallon of water for sucessful control. You can usually find a surfactant at any local feed and fertilizer. Look for 90 % surfactant. You dont absolutely need surfactant but it will help.

thats my take

A 12.5 to 25% REWARD:WATER solution might be a little stout. You would only be able to use 16 to 32 gallons of this mix per acre (.37 - .75 gal/1K sq. ft.) while staying within labeled use-rates. That can be a tough challenge with hand-held equipment, without creating a drift-prone spray pattern.
Though everyone treats with widely varying water-volumes, 4 oz. of REWARD per gallon of water, applied at roughly 1.5 gal. of mixed-solution per 1K sq. ft. should be very effective. As mentioned above, use very clean water to mix with the REWARD. Also, CIDE-KICK II (d'limonene) @ 1 oz./gal. of mixture works wonders with REWARD.
ALSO: WEEDTRINE-D is a much diluted formulation of REWARD, with a price tag that may be a more easily digested by pond owners with less than 1/4-acre to treat (though much more costly per lb of active-ingredient). However, mixing rates for WEEDTRINE-D do need to be adjusted (upward) to allow for its lower amount of formulated active-ingredient.

good call KM,

I totally forgot about weedtrine, dont use it much. dont spray 1/4 acres ponds much.

We don't even carry WEEDTRINE-D, since it really is an expensive alternative to REWARD (except for very small treatment areas). But, it is an alternative to be considered.
BTW: There are some water-use restrictions that need to be observed with either formulation of diquat: namely livestock, irrigation and domestic uses. Terms of the use-restrictions are based on application rates; so read the label before buying the product.

This is the first year we are getting Duckweed. Our pond is about 1 acre and 13 years old. I'm not sure what causes this weed but any info in what causes it, how to track down the source and any control would be greatly appreciated.

Diana,

look no further than the name, its transported by ducks, geese and other wading birds. One small duckweed plant under the right conditions will replicate into a serious problem

Diana,
If you duckweed problem gets bad, I would NOT go with Reward or other spot treatments. If you are like me you want to get rid of the duckweed so you can enjoy see "water" on your pond. Reward will not give you that solution. See my other post for reasons.

Guy

GB,
I see your point about the Reward but there are many situations where its the only option so I would discount it all together. sonar or avast will eradicate duckweed but if there is a good sized stream feeding the pond those products will not work. Reward is excellent at killing duckweed, it rarley eradicates the problem but I have eradicated duckweed with Reward. 95% of the time you need to look at Reward treatment on duckweed like mowing the grass, it has to be done often to keep it in check.

GB
If Reward isn't a option what do you suggest. My pond is completely covered and I'm getting worried about a possible fish kill.

diana
I wish I knew! I'm just a person with a pond like you. I tried keeping up with the reward treatment like Shan said.

But after a while it seemed that reward was not even working. The first few times the DW (duckweed) turned brown and was easy to see was dead. But the last few times I have sprayed I have seen no change.

Even when you do kill it it stays on the pond until the next heavy rain washes it away. I tried reward for close to four weeks and out of that time, I had a clean looking pond maybe 3 days. And that was after the first spraying.

I may try Sonar next year but I'm not sure how to proceed. I post a question (Tried Reward... now what) but have not got any replys.

Good luck to you Diana, if you learn something PLEASE let ME know!

GB,

are you mixing your spray mixture with pond water. if so try it with clean tap water, also use a good surfactant.

Sonar or Avast will eradicate duckweed as well as all the other aquatic plants in the pond. just simply pour it in the pond in a few places, it will do the rest. the only drawback to these chemicals is that they are very slow acting, it takes around 90 days to see results. so if the pond has a creek feeding it, the herbicide will probably be washed out before it has a chance to work. If your pond has no creek coming in and a small amount of water flow then Sonar or Avast will work great.

Also if you have flowing water you can keep adding Sonar/Avast monthly to keep the floridone concentration high but its very costly.

In high flow rate situations you can setup a temp. siphon or rent a pump and pump the pond down a few feet prior to Sonar app. We then treat the exposed shoreline with Reward to kill duckweed on the edges. When this has been done SOnar has eradicated 83% (5 out of 6) of the ponds heavily infested with duckweed. We have also eradicated it when the pondowner stays on it with Reward and surfactant at proper rates. Good luck, I hate it for pondowners when all of a sudden they have duckweed and are forced into spending some serious time and money to have their pond back.

Shan, I have been using well water to mix and added CIDE-KICK. And like I have said, even if I went out and sprayed every other day I would still need to rely on a heavy rain or skreet it to get a nice looking pond.

I think at this point I have conceded defeat once again for this year. I will try SONAR early next year and pump down the pond like Greg suggests. How long can I expect Sonar to last, I have heard it is good for 4 to 5 years. My pond fills with runoff so any rain I get, the pond fills pretty quik and then runs out once full. Will that cycle out the treatment after the first year?? If so I think I may be SOL. I can't afford to spend $500.00 plus on my pond every season. It would be cheaper in the long run for me to fill it in and have a nice little water garden.

thats weird, I have never heard of Reward not working on duckweed. Are you sure its duckweed. there are several types of floating plants. one common problem I have when folks call is mis-identification of plants

with that said, you need to figure out how much water if flowing out of the pond. catch the water in a bucket and time it. lets say you get 5 gallons in 5 seconds. thats one gallon per second. mulitply that rate out to see how much water is flowing out of the pond in one day, then one week then one month.

one acre of water 3 feet deep is about 1 million gallons of water. figure out how much water is in your pond. once you know how much water is in the pond and how much is flowing out you know how long it takes for the pond to flush. Add recommended rates of Sonar or Avast a week or so before the pond is flushed.

Sonar does not last for 5 years, I dont have a label in front of me but I think its more like 18 months, provided the pond does not flush. Draining the water can can help but it depends on how much water flow you have. if you drain it down and it fills back up in 2 days I would not worry about it, wait for the dryest part of the year, treat, and hope it does not rain much.

GB I think the key is having a good concentration of SOnar for the first thirty days. I try all efforts to increase that chance, draining and watching the weather. If it is going to rain heavy in a week, wait. ALso better to treat before it gets too hot. Kelly Duffie may add a comment on this, but I feel SOnar can work great on Duckweed under the right circumstances, (best way to eradicate). However, I find it hard to believe it will stop duckweed or other invasive plants after about 6 months of the application, much less 5 years, I mean how is it concentrated enough after the pond has received flows for a few months?

Well with your two comment I think I am just out of luck. There is no way I can afford to treat with Sonar unless It's going to last a few years.

What I don't understand is how I can drive a few minutes down the road in any direction and see a number of nice clean ponds of all sizes (smaller and lager than mine).

Why the hell don't they have a weed problem!

I really hate it. The pond is an eye sore except for about the two to four weeks after the ice goes out.

I don't know if I can get the white carp I see people talking about here or if it would even help. I know I would have to restock eack year due to freeze out.

I dunno, I think if I can find a constuction site looking for a place to get rid of clean fill, I may just have the perfect spot for it.

Sorry to keep bringing bad news but the grass carp will not control duckweed, either. I see ponds that are right beside each other, one with a weed issue the other just fine. That is what keeps this job interesting.

GB, I think I read most of the replies to you problem but the duckweed has to be feeding on something. Is it possible that a septic system is close to your pond and feeding it?

FH

Yea it gets plenty of food. The whole pond is filled with runoff from numerous neighberhood yards. I mentioned that my very first questions the this forum. I said I could could probable re route the runoff to go aroun the pond. But it seemed most thought the fertilizer that I would be getting from the yards is only a small part of the problem.

If I remember correctly from my college Botany, the main limiting factor for duckweed is phosphorous. You could add aluminum sulfate to the pond to strip it out, add a bacteria blend especially to reduce phosphorous(I think I saw some in Aquatic Ecosystems), and try to limit new influx in the future.
Robert B