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5-mm-shiny-emerald-beetles-only-on-polygonum-donald-lowdnes

I have searched the internet and found many similar beetles (rose beetle, june beetle etc)  but none so small and eating ONLY the polygonum which is generally supposed to be pest and disease free.  What are they?  They are no more than 5mm long and bright metallic emerald with black underparts.  Antennae are fairly long, flexible and made up of a string of tiny blobs when you look with a magnifier.  They do not fly away but drop to the ground and play dead till you've gone.  Is it a foreign import that likes our hot summer - is it potentially part of the answer to Japanese knotweed - or is it just something common and nasty I just haven't noticed before?

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  • nutcutletnutcutlet Posts: 27,166

    They sound interesting. Have you got a photo?



    In the sticks near Peterborough
  • Yes.  I will have a go at attaching one.  This one opened its wings since it wasn't happy to be photographed so it looks a bit longer at the back than when the wings are completely stowed.  The ruler shows cms.

     

    image

     

  • waterbuttswaterbutts Posts: 1,214

    There is a wonderful website called Whatsthatbug and, although it is based in the USA, there are lots of other creatures mentioned on it.

    The nearest thing that I could see after a brief look on the website was a leaf beetle of the order Chrisomelidae.

    It is great fun to look at this website as the people who run it are quite eccentric.

  • Thank you.  I've had a look and it does look at lot like the dog bane beetle (although their picture gives no size).  If so, why is it here?  Anyway, I have sent the picture to them so see if I get a response.  Maybe I'll put some in a container and send them to the RHS.

  • waterbuttswaterbutts Posts: 1,214

    I think a photo would suffice!image

  • If I get any replies to my enquires hither and thither - I will let you know.

  • waterbuttswaterbutts Posts: 1,214

    image

  • waterbuttswaterbutts Posts: 1,214

    Do you know, I have just returned frodm a day's walking in the beautiful Derbyshire Dales and have seen no less than three of the pretty little beetles on the way. They were all on dock plants and, I don't know if the two things are linked, all the leaves of all the docks were a complete lacework pattern with only the veins remaining.

    Also saw dozens of ladybirds and ladybird larvae, which was very cheering as there are very few to be found in my garden.image

  • Yes they are very pretty but I have to admit I disposed of hundreds of them yesteday by digging up all the polygonum and putting it on the bonfire.  I did feel sorry in a way but the plants were covered in them and, as you say, progressively turning into lace. Pleased to say one ladybird crawled out as I was digging so I rescued her and put her among the Rosa Rugosa. 

    No word yet from the experts.

  • I got a very full reply finally from the RHS.  It is a green dock beetle so you found them in their proper place.They have two generations between April and September and they are keen on rhubarb!  Fortunately they didn't notice mine!

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