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Duckweed devourers

Printed From: Reptiles and Amphibians of the UK
Category: General
Forum Name: Associated Fauna and Flora
Forum Description: A forum for plants, invertebrates and other animals associated with herpetofauna
URL: http://www.herpetofauna.co.uk/forum/forum_posts.asp?TID=5151
Printed Date: 23 Sep 2017 at 3:16am
Software Version: Web Wiz Forums 11.06 - http://www.webwizforums.com


Topic: Duckweed devourers
Posted By: Suzi
Subject: Duckweed devourers
Date Posted: 17 Jun 2017 at 7:26pm
My small pond was more or less covered in duckweed with pondweed growing through it. There was very little free water. Within a matter of days the pondweed has disappeared except under the shade of surrounding plants that flop over the water. This seemed to me quite amazing, knowing what a devil it is to get rid of manually. I had noticed a few little creatures moving slowly across the surface that appeared to be caddis larvae with duckweed as their casing! Today I did a dedicated sit by the pond to watch, as now the pond weed is being eaten - big circular areas missing from leaves, some eaten altogether. As I sat I saw plenty of these surface feeding creatures eating the leaves. They seemed to also have a long tube (maybe tubes?) that occasionally came out of their head end. This pond is about ten years old and I've never had anything like this before. I reckon it will be stripped of pondweed within days at this rate. 
I am hoping someone has some idea what these little chompers are called, as I can't find them in quick Internet searches. I won't interfere in the balance of things, and will let them carry on. Presumably newts don't eat them, or frogs. My larger pond doesn't seem affected yet.
Appreciate any help. Tomorrow I might net one out and photograph it.


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Suz



Replies:
Posted By: chubsta
Date Posted: 17 Jun 2017 at 9:43pm
Whatever it is i would love to have some! My duckweed isnt too bad since i cleared the pond - it started to come back but i put two fountains in and the disruption to the water seems to have killed most of it off, however, i have had to switch them off for a while as i think it was also affecting what few tadpoles i have left.

If your critters are a natural Uk species then you could be onto a goldmine!


Posted By: Suzi
Date Posted: 18 Jun 2017 at 11:15am
I've been out this morning and collected a few of the creatures and photographed them. One seems to have made itself a casing of pond weed leaf and the other two look like duckweed plus other bits. There are plenty of them scooting along the surface to feed. The shot of the pond isn't too useful as I hadn't got a before view. All this happened so quickly I was a bit stunned - a matter of days. Before there was plenty of pondweed and frogbit and duckweed. The one pence piece is for scale.










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Suz


Posted By: Iowarth
Date Posted: 18 Jun 2017 at 10:36pm
Certainly a million miles from my area of expertise but how about these / http://www.ukmoths.org.uk/species/cataclysta-lemnata/mid-instar-larva-and-case/" rel="nofollow - http://www.ukmoths.org.uk/species/cataclysta-lemnata/mid-instar-larva-and-case/

all the best
Chris


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Chris Davis, Site Administrator

Co-ordinator, Sand Lizard Captive Breeding Programme (RETIRED)


Posted By: PondDragon
Date Posted: 18 Jun 2017 at 11:27pm
Possibly 2 species - Chris's suggestion eating the duckweed and the Brown China-mark eating the pondweed & frogbit: http://www.ukmoths.org.uk/species/elophila-nymphaeata" rel="nofollow - http://www.ukmoths.org.uk/species/elophila-nymphaeata

There is a small wasp that parasitises these so look out for that running round on top of the pondweed on sunny days.


Posted By: Suzi
Date Posted: 19 Jun 2017 at 9:11am
Thanks guys! I would never have thought of moths!

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Suz


Posted By: Suzi
Date Posted: 19 Jun 2017 at 12:01pm
PS Stepped out this morning to see all traces of duckweed now gone. 

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Suz


Posted By: will
Date Posted: 23 Jun 2017 at 6:22am
as with Chubsta can I have some please?!  lucky you Suz, I'm heartily sick of the daily chore of scooping out duckweed from the pond.


Posted By: Suzi
Date Posted: 23 Jun 2017 at 7:36pm
Much as I loathe duckweed I've discovered in my ponds it is the go to place for newt larvae. When it forms big blobs with other weed in amongst it, they really seem to love it. An even layer of it on the surface doesn't seem to hold the same attraction. I guess the moth munchers when they've finished all their eating they change and leave the pond, so not much use as a long term duckweed devourer. Nice thought though!

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Suz


Posted By: Suzi
Date Posted: 18 Jul 2017 at 12:25am





Taken just before midnight tonight. There has been a lot of frog activity this week with more jumping into the ponds and some croaking during the daytime.
These two were sat on the anti-blackbird netting which I can now remove. It was placed to make it more difficult for them to flick newts out to feed their young. The netting had been above the water but has recently been disturbed. This is the pond that was heavily covered in duckweed, but now is bare of it except two small pinhead pieces.


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Suz


Posted By: chubsta
Date Posted: 18 Jul 2017 at 4:23pm
Great news! It seems there is hope after all, funnily enough my duckweed problem has been sorted too. After draining the pond i refilled and immediately the duckweed started growing, but i removed as much as i could each day. I got quite a few different plants from the garden centre, but also from my local canal, and now have only a few very small clumps of duckweed left, although it still grows it doesnt thrive and it shows no sign of being a problem.

What is nice about our two ponds i guess is that the problem has been solved naturally, no chemicals etc, just letting nature take its course and finding a solution itself.

Will be very interested to see if you get those caterpillars back next year too, i never knew that moths would have aquatic caterpillars.



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