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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?

Posts

  • nutcutletnutcutlet Posts: 27,445

    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

     

  • 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.

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

  • 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!

  • Fascinating!  Thanks for letting us know - I shall keep my eyes open for them on dock leaves. image


    Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.





  • LynLyn Posts: 23,190

    Thank you for finding out what those beetles are called, i had searched the net and could only find the small scarab.

    I have found these on dock and my rhubarb was covered.

    I have sprayed them with Baby Bio house plant insecicticide, they just dropped of dead instantly.

    Gardening on the wild, windy west side of Dartmoor. 

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