Duck weed

[LindaB]

Those of you that have large volumes of water covered in duck weed might find a biological solution by searching on the net for control by weevils.

It has been found that one weevil in particular is being used to control/eliminate Azolla called 'Stenopelmus rufinasus'. I dont know if this one will work on duck weed, but there has been success with Azolla (fairy moss).

It might take a little while to find the information you want by searching the net, but its worth a go.

I am eagerly watching a small pond near where I work that has been infested with Azolla this year to which the above weevil was introduced two weeks ago. Its not a quick fix but from what I have found out, it works. Obviously is depends on water volume, thickness of the weed and how many weevils are introduced.

Worth a thought.

Linda

[Dogghound]

Why do you want rid of the duck weed? they are a good food for waterfoul, can remove nitrates, are good cover for invertibrates, small fish, tadpoles etc, as well as larger amphibians and fish. Duckweed also reduces evoporation.

[Autotech]

Originally Posted by fbcpmike

I'd like to know what the chemical is if it exists.

Usually there are regulations about using chemicals within certain distances of ponds and water courses, you will have to talk to the Environment Agency before you go ahead as you may need a licence.


It's a floating plant so is moved by winds and other effects, as for killing off, we still have our fish but lost a couple of large ones because of the oxygen levels.

Let us know how you get on, it's a problem in many places and info is always usefull.

"Roundup" is a chemical that kills Duckweed and is suitable for Aquatic use. It can be purchased from Scats

[fbcpmike]

Originally Posted by Autotech

"Roundup" is a chemical that kills Duckweed and is suitable for Aquatic use. It can be purchased from Scats

Roundup® is a terrestrial herbicide that will adversely affect aquatic environments. As a voluntary custodian of our park I would be prosecuted to an inch of my life if we used a Glyphosate product on or close to a water body. You will need an Environment Agency licence to use Roundup® anywhere near a water body.

Lethal effects of Roundup® on amphibians - Roundup
Factsheet - June 2004 - Glyphosate factsheet

[fbcpmike]

Originally Posted by Dogghound

Why do you want rid of the duck weed? they are a good food for waterfoul, can remove nitrates, are good cover for invertibrates, small fish, tadpoles etc, as well as larger amphibians and fish. Duckweed also reduces evoporation.

Our pond is nearly an acre in area, one eight of the total area of the park. It has been infested with duckweed for the last 3 years, previous to that it had been clear of such invasive weeds for probably 60 years. A duckweed covered pond is not the natural state and whilst it can remove the nitrates its own decomposition will basically put them back, nitrates need removing at source by non use. As for the wildlife, ours were quite well and thriving before the duck weed in spite of the Terrapins, we got rid of them as well, the duckweed is not so easy.

What we have now is a green rank smelly oxygen depleted pond with floating dead fish.

Linda B, I'd be in very interested in the results of your local pond with the weevil introduction.

[Chiltern Chris]

Originally Posted by LindaB

It has been found that one weevil in particular is being used to control/eliminate Azolla called 'Stenopelmus rufinasus'. I dont know if this one will work on duck weed, but there has been success with Azolla (fairy moss).
Linda

Hi, Just for info. the weevil is Azolla specific and won't touch duckweed. All biological control methods whether they're fungi or invertebrates must be species specific or they may go on to create havoc in the countryside.

Also Roundup is a glyphosate based herbicide (made by Monsanto - a good enough reason not to buy it!) and although it is licensed for use in water and does kill duckweed, it can also kill all other plants in the pond and so you have a major risk of destroying the pond's ecosystem if it's used. So if you do use it, be very careful.

Chris

[LindaB]

Originally Posted by fbcpmike

Linda B, I'd be in very interested in the results of your local pond with the weevil introduction.

Hi there. Well, this is the third week now and until today, no change. A huge surprise this lunchtime, it has started to fragment and small areas of water are now visible. I am hoping that I can take some photos tomorrow if the weather is dry during my lunch break. I am keeping my fingers crossed that it is the start of it clearing. I have some photos that I will upload on here when I get time of the original pond, the mass covering at present, and how it progresses. There is an excellent article I found of a newsletter where this weevil was used, I believe we cant do links on here so do a google search, and its a Thames Water newsletter - the relevant pages in that newsletter are very interesting.

In response also to Chiltern Chris' comment that this particular weevil is Azolla specific, yes I know, I did mention that in my original post, but like I also mentioned, there just might be one specific to Duck week. Doing searches and asking relevant bodies is the way to find that out. English Nature may be able to offer some advice. Its worth investigating all the same. Also for anyone else reading this thread that has the Azolla problem, it offers some light at the end of the tunnel by using biological control.

I certainly hope you can find one for duck weed, its a very depressing sight seeing a pond totally covered in an invasive plant and even more upsetting for the wildlife of that water. I understand your plight, and even in this smaller pond, when the moorhens or ducks disturb the weed, I can smell the water starting to get foul. There are no dragonflies around it either at the moment.

Regards
Linda

[kaitkaitkait]

How fast does duckweed grow? I don't have it in my ponds, but there's a bit of it in one of my quarantine tanks - it came off some other plants.

I'm wondering if some sort of continuous water pressure would at least clear some of the surface on the lakes and ponds people have mentioned. Could a pump be set up - a solar one perhaps?

[Rich]

I have two ponds linked by a waterfall. The waterfall leaks so I leave it off most of the time. When the top pond, which has no fish, gets clogged with duckwed, I simply turn on the pumps and let some of it flow into the bottom pond.

The rudd go mad for it and the water boils as they eat it before it can become established. I have never seen it in the lower pond.

[fbcpmike]

Originally Posted by kaitkaitkait

How fast does duckweed grow? I don't have it in my ponds, but there's a bit of it in one of my quarantine tanks - it came off some other plants.

I'm wondering if some sort of continuous water pressure would at least clear some of the surface on the lakes and ponds people have mentioned. Could a pump be set up - a solar one perhaps?

Given good conditions, VERY quickly. On the pond in our park (3/4 acre) it grew from almost nothing, a couple of square feet, to the whole pond in about 2 weeks. It grows to a point where it stabilizes to basically a mat of vegetation about 1 inch thick with another 2 - 3 inches of roots underneath. So if you leave it, it will reach a point where it stops, clear a large patch and you will encourage its growth. Apparently it does not like moving water or dense shade.

You stand a chance of getting it out of a tank with a net, but you do have to get every last bit.

[Capperman]

I have three small garden ponds, all with duck weed. I have tried all the usual methods but i have so far failed to get rid of it. My preferred method to control is skimming with a small fishing net whereby i can remove about 90% in a fairly short time. Recently I purchased a duckweed treatment from my local garden centre (i don't think i can name it due to the rules) but it is supposed to be a bacterial control which is meant to restrict the sub dividing of the plant by altering the chemical balance of the pond. It hasn't been very successful so far, but i'm still hopeful. Due to the price i don't think it will be viable for larger ponds/lakes.

[Zildjian]

The duck weed on my half acre pond seems to have cleared completely! This time last year the entire pond was covered in the stuff.

[fbcpmike]

Originally Posted by Zildjian

The duck weed on my half acre pond seems to have cleared completely! This time last year the entire pond was covered in the stuff.

This year we too are free of the dreaded Duckweed except for a very small area near the outfall, fingers crossed if it this lasts another 6-8 weeks or so then should be totally clear for the year. Last winter was a cold one for us here, the pond was frozen for 3-4 days over several periods and that killed off most of the duckweed, the Geese have kept the remainder in check. We hope that it is not re-introduced by the local ducks who fly between several other ponds.

[dampflippers]

I know this thread is really old, but a message to everyone:

Please NEVER NEVER add any sort of fish to a pond without approval of the owner.
It is illegal and can completely ruin a newt pond, and once fish are in they can never be removed without completely draining it.

[Capperman]

Read your message re newt ponds. In what way do the fish ruin these? Is it just the eating of tadpoles? I have introduced two small fish into one of my ponds which I know contains newts, in an effort to control midge lava. Do you feel this was a grave mistake, and should I remove them straight away.

[dampflippers]

Good newt ponds need to be fish free.
Fish and newts can coexist, but the fish will eat the eggs and newt tadpoles, so the population will not thrive or increase.
A fish free pond will have a much greater biodiversity and wildlife value because of the lack of predators.

Regarding your 2 fish- hopefully they won't cause you too much problem. If you already have newts, they love midge larvae as do water beetles, their larvae and dragonfly and damselfly nymphs. Keep an eye out to check the newts still lay eggs- look for folded water foget me not leaves, and look for the tadpoles by dipping a white marg tub into a weedy bit and examining the contents.
If it was sticklebacks though, I would definitley remove them now before they start to breed. I have sticklebacks in one pond, and not in the other. I get newts in both, but have hardly ever found a baby in the one with sticklebacks, whereas I get loads in the other.

I have just been doing a garden pond survey in my local area, and initial analysis show that no ponds with fish and a filter have more than an odd newt, and only one pond with fish (but no filter or pump) have an abundant newt population.

I hope those terrapins someone mentioned were removed in a permanent way rather than being rehomed into the wild where they are very voracious (which is illegal and causes big problems in natural ponds too).

[Capperman]

Originally Posted by dampflippers

Good newt ponds need to be fish free.
Fish and newts can coexist, but the fish will eat the eggs and newt tadpoles, so the population will not thrive or increase.
A fish free pond will have a much greater biodiversity and wildlife value because of the lack of predators.

Regarding your 2 fish- hopefully they won't cause you too much problem. If you already have newts, they love midge larvae as do water beetles, their larvae and dragonfly and damselfly nymphs. Keep an eye out to check the newts still lay eggs- look for folded water foget me not leaves, and look for the tadpoles by dipping a white marg tub into a weedy bit and examining the contents.
If it was sticklebacks though, I would definitley remove them now before they start to breed. I have sticklebacks in one pond, and not in the other. I get newts in both, but have hardly ever found a baby in the one with sticklebacks, whereas I get loads in the other.

I have just been doing a garden pond survey in my local area, and initial analysis show that no ponds with fish and a filter have more than an odd newt, and only one pond with fish (but no filter or pump) have an abundant newt population.

I hope those terrapins someone mentioned were removed in a permanent way rather than being rehomed into the wild where they are very voracious (which is illegal and causes big problems in natural ponds too).

Thought you might like to know, both fish have now been removed to a more suitable pond as a precaution. It would be upsetting if I were to harm my newt population.