30 Apr 2012

Rosemary Beetle

Edited to add: Be on the lookout for this garden pest if you grow herbs such as sage, lavender, rosemary, mint... and even thyme. One London reader, whose rosemary was host to a colony of these beetles, commented, "from noticing the first little bites on the plant, it only took about a week for it to be totally beyond rescue." Vigilance and daily checking are key.

Rosemary Beetle

Do not be fooled by the attractive plumage of this beetle. This handsome fellow is a predator of the first order and should be destroyed on sight. I spotted him yesterday evening when, as the sun came out, it just glinted off the shiny back of the insect.  I was looking over the various herbs in my patch and was lucky to be in the right place at the right time.

Although undoubtedly very beautiful to look at, I remembered seeing a warning poster during my day out at Jekka McVicar's herb farm and I was certain this could be the very culprit. It was the bold jewel coloured stripes that reminded me so I continued to squish and search by hand brushing through my herbs.  I found three in a short space of time.

Rosemary Beetle
~ My thumb gives an idea of the beetle's size ~
The adult rosemary beetle, also known as Chrysolina Americana, feeds on the new growth of lavender, mint, sage, rosemary and thyme. In short, you could have your entire essential kitchen herbs wiped out in a season. As the beetle seems to prefer to feed on Lamaceae plants, it's thought that others in the family may also act as hosts to this pest. Rosemary beetles originate from Southern Europe and were first seen in the UK in the early 1990's; they are now prevalent across the country. More info on the RHS site here. They are destructive enough to warrant the RHS carrying out research on this bug - there is an ongoing survey so, if you are unfortunate enough to find this beetle in your garden, please take a photo (if possible) and complete the online form. There is a link to the survey on the RHS page about the beetle.

I spoke to Jekka today who confirmed my suspicions.  She farms all her herbs organically and suggested the following method of control:  Get hold of a yellow sticky trap (a google search will offer plenty of outlets or ask your local garden centre), peel back one side to expose the sticky surface and lay it flat on the soil under the infested plant, sticky side up.  Gently tap the plant so that the beetles fall onto the trap. Destroy.

Jekka also reminded me that the RHS are the only people doing valuable and essential entomological research on this subject and, as gardeners, it's vital that we support the RHS, if we can, by becoming members - with the bonus that you can get entry into some spectacular gardens and get lots of advice, if needed.

Unfortunately for me, London is flagged up as one of the main areas where these beetles have established colonies. I didn't know until recently to look out for these beetles but will now be extra vigilant - and I've joined the RHS.  And now for the close up:

~ Beautiful but deadly for herbs ~

24 comments:

  1. It's such a pity such a beautiful bug causes so much damage. I have yet to come across them, fortunately. Maybe Wales is a bit wet for them!!! I'm sure with our changing climate and milder winters it won't be long before they're here though. I think the RHS is a brilliant organisation, it has it's flaws but then nothing is perfect. I used to be a member when we lived near London, we used to go to Wisley quite a bit but over here in Wales there aren't so many gardens available to us. It's the same with the National Trust. The garden magazine is good though so I may drop unsubtle hints for membership for my birthday!

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    1. I would never have known about this insect if I hadn't seen the poster at Jekka's farm. I've been keeping an eye open but haven't seen any more - yet! It's very cold here at the moment so perhaps they've all gone somewhere a bit warmer for the time being. The first colony in London was discovered by Waterloo Station, a warm place if ever there was one and ideal for onward travel!

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  2. I've never heard of this or seen it before - thanks for the tip off - I will be vigilant. There is always something out to get us gardeners one way or the other.

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    1. Oh don't I know it! I'm already battling aphids on my borage seedlings on the balcony and they've got one of my mints as well. So far the sacrificial nasturtiums, just sprouting their first leaves, are aphid free!

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  3. Thanks for the warning, have just been out and checked my rosemary and other herbs, nothing to see so far, but will now do regular checks. As you say, very beautiful, just like the red lily beetle, but there is only one course of action!

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    1. It does seem such a shame to destroy such a beautiful creature - perhaps that's why they've prevailed in the garden! Knowing what damage they can do definitely strengthens resolve!

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  4. They always remind me of oil floating in a puddle. It's so annoying that there's so many pests just waiting to devour our plants.

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    1. Ah, so you've encountered these beasties before then, Jo? I hope you didn't discover them after they'd damaged your plants! I feel I don't know enough about garden bugs - it's a topic I obviously need to know more about!

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  5. Thanks for the tip off Caro- that's one beastie that I've not heard of let alone encountered but no doubt is will spread north. I will be prepared to do battle now. Here's yesterday's warmth after Sunday's deluge bought out the dreaded but attractive lily beetle. Disposed of two but the third which was on a lily when spotted escaped my clutches!

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    1. I've just had to look up the lily beetle Anna - bright red so should be easier to spot than others. I only have a few lilies in the veg garden, they were left over from a massive clump that we had to get rid of as they were entangled with ivy roots. I rather like the ones that are left so will now have to be vigilant for the lily beetle as well! (And I've spotted green shield beetles aka stink bugs. They're sap suckers so also need to be moved on!)

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  6. They look so pretty with those colours but can apparently wreak absolute havoc . Great photos!

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    1. Thank you SVG - It was fortunate that I'd got my camera with me; 18 million pixels means you can get in quite close! I'd rather see them in photos than on my plants though!

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  7. Thank you for highlighting this pest - you're right, they are beautiful, but so destructive. We had a problem with them in our last garden which was just outside London - but only on rosemary - they steered clear of the other herbs, but then again, we had quite a lot of rosemary! It's rotten luck to find yourself in a hotspot for any pest. I was interested to learn about how Jekka deals with them... if we find any here in Norfolk, we'll know what to do - thank you.

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    1. You're very welcome, I think that's the beauty of the web, advice can be passed along quickly. Interesting that you've already had to deal with this pest so will be on the lookout. I hope they leave you alone in Norfolk although please let the RHS know if you find any!

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  8. Mmm I was watching bees on the rosemary flowers on Monday before I was aware of this beetle. Next time I shall have a closer look and hopefully not find any!
    Thanks for such an interesting and informative post even though, or perhaps especially as, it conveys bad news for gardeners. Flighty xx

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    1. Thanks Flighty, Lovely that you're already seeing bees but I don't think we'll find many bees this weekend - it's rather chilly here in NW5 and I'm leaving my balcony mini-greenhouse firmly zipped up! I think the rosemary beetle will also disappear for a short time, they like the new growth on plants so you might not find any for now but it's worth mentioning at the allotment shed store and to other plot holders. They mate in autumn so their second feeding time is around then, another time to keep a look out! Caro xx

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  9. A few years ago my rosemary was completely destroyed by these beetles. Be careful and check plants as often as possible - from noticing the first little bites on the plant, it only took about a week for it to be totally beyond rescue. I live in London too and I have heard that they are very common here. Have got some lovely lavender in my garden but thankfully they haven't gone for that, only seem to be after the rosemary in my case.

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    1. Hi Kristina, lovely to meet another London blogger and thanks for commenting; it helps to round out the picture of what we're up against when we hear personal evidence of the havoc this bug can wreak. I'm sorry to hear about your rosemary, such a useful herb. I've been checking ALL my herbs on a daily basis but haven't found any more yet. I doubt that I've seen the last of them though!

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  10. I live in North London and woe is woe just spotted my first ones of the season this evening. I swiftly dispatched about a dozen but will remain vigilant. Having lost a load of rosemary plants a year or two back I'm aware of the damage they cause.

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    1. Ah, interesting... another suffering Londoner. You probably know a lot more than I do about this pest! I've seen a few more since writing this post and I immediately "despatch" them to their doom. Same with the red lily beetles that I discovered getting frisky under the lily leaves! This warmer weather seems to have brought all the bugs out and I'm just glad that I'm seeing them so able to take action! I hope that your rosemary survive this time...

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  11. Despite their beauty, I hate these pests!

    I'm a West Londoner and had last year's lavender, rosemary and sage plants destroyed by these beetles. I finally just gave up and replanted all three this year with the vow to be extra vigilant. Despite this, from day one I've had to face twice-daily pickings and yet they still keep turning up -- I'm at a complete loss about what else to do!

    My nursery has told me that hand-picking is the most effective form of control but I've also read that perhaps a lemon/soap spray might be a deterrent. I'm curious if anyone else has heard this?

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    1. Hi Christine, thanks for commenting. Frankly, anything is worth trying. I've been handpicking them off (easily finding 3 or 4 a day) and stamping on them but only finding them on the mint which is strange as this is growing close to lavender and rosemary!
      I've used a weak Ecover solution on blackfly which has been very effective as the aphids can be sprayed directly. The problem with this beetle is that, if found, the only solution is to immediately destroy - spraying might not target the beetle and you'd just have very clean herbs! It might be worth pouring a lemon solution around the base of the plant to deter any grubs in the soil.

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  12. oh i have them on my rosemary plant in the garden, luckily we do not eat the plants in our garden as we privately rent and someone who use to own this house made a vegtable patch

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  13. Thanks for your informative post. Even though I'd seen this on my Rosemary for a long time, I had absolutely no idea it was a pest and thought it was just a harmless beetle. When I noticed my Rosemary was looking eaten and very sad, I decided to cut it right back hoping this would improve things (it hasn't) and happened to be browsing the RHS website for something completely different when I came across the Rosemary beetle by pure chance, and now realise it is the culprit of my sad looking plant. It is completely smothered in beetles (only today I saw lots) so doubt very much it's going to come back to its original healthy condition, although I will try the various suggestions I've read online. I completed the RHS website questionnaire to inform them I have it on my plant and my location (SW London btw).

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Caro x

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