What killed my mint?

I know the answer to this question, but first I will explain the scenario.  One of my potted mints had been looking increasingly ill of late and yesterday when I moved the pot the foliage simply separated from the potting mix.  Something had eaten its roots, all of them.  Mr 2 and I investigated and all through the pot we found these white curl grubs.  I think some people call them witchety grubs but that’s not really accurate.  The grubs are grey and white in appearance with an orange head and they are usually found curled in a foetal like position.  Hence the name white curl grubs I guess.

There were close to 50 of the things in a 30cm pot.  This was high density larvae.  No wonder all the roots got eaten.   Mr 2 was exceptionally pleased with them.   They are currently residing – complete with dirt- in the back of Mr 2’s ride on Scoop (Scoop is a character from Bob the Builder).   I’m not sure exactly what sort of beetle these particular ones would have metamorphosed into (from what I have read they are most likely to be scarab or cockchafer beetles) but I wish I had some chooks to feed them too.  They are, apparently, very high in protein.  I have noticed quite a few of these grubs when I’ve moved pots sitting on the lawn but I haven’t thought much about them.  My understanding is that they are only really destructive in pots or when in particularly high concentrations in lawns or garden beds.  I think I will spend the next few days inspecting my other pots – to lose some mint is one thing, a dwarf citrus would be something else entirely.

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31 Responses to What killed my mint?

  1. Daphne says:

    I would have guessed Japanese beetle grubs. I see them occasionally in my soil. Here and there. But I’ve never seen them in such a concentration.

    • Liz says:

      I was amazed how many this pot produced. They certainly aren’t nearly as many in my garden beds – I guess its much easier for the birds to find them in the beds though.

  2. Bummer! Sorry for your mint… Thanks for this post, I had no idea this could live in the pots. I need to go check my citrus too.

    • Liz says:

      Neither did I until yesterday – I can’t believe quite how many there were living there. I guess mint does have quite a juicy root system.

  3. Mark Willis says:

    Yuck. These are what we call Chafer Grubs (Google it!). The adults are beetles called Cockchafers. These days you can buy nematodes that kill them.

    • Liz says:

      I think you are probably right but there also seem to be a number of other beetles with very similar larvae. Scarab beetles larvae is quite similar as are Christmas Beetles. i would like to think these are Christmas beetles but i suspect they are boring cockchafers instead.

  4. Frogdancer says:

    Ohhhh…. I’ve got a couple of pots of mint that are looking sad. Must go and check. Thanks!

  5. Oh no…those little devils just deprived you of some awesome mint. The silver lining is that mint it’s so easy to grow that you’ll have you’re pot at full capacity in a heartbeat. Even I can manage to grow mint, and I forgot to water it regularly…

  6. Cockchafer grubs are usually found in lawns – are you sure that they aren’t vine weevil larvae see here http://www.dgsgardening.btinternet.co.uk/vineweevil.htm which are often found in containers and feed on the roots of almost any plants.

    We have had vine weevils in pots but never in such large amounts. I found blackbirds relish them.

    • Liz says:

      I have the same bugs all through my lawns too. I looked at your vineweevil and the grub looks a bit different. Mine has a very distinct grey back and I think it would produce a larger beetle than a vine weevil. Having said that I may be wrong. I have to say I have enjoyed finding them (the mints death notwithstanding) as I have learnt a lot about grubs in the process.

  7. Nina says:

    They look like what I usually call cockchafers or cut worms and yes, they are destructive, whatever their name. Gosh Liz, you have more than your fair share of pests at the moment. What suburb do you live in? I’ll be sure to steer clear, I’ve got enough of my own! :))

    I’m happy to say, that now the cooler weather has come, the whitefly aren’t nearly as prolific as they were. As happens, there’s probably something else lurking to take their destructive place, though. Ah, the joys of gardening.

    • Liz says:

      Coburg – although funnily enough the things that others seem to be struggling with at the moment – white fly and the white butterflies both seem to have passed us by theis year.

  8. VP says:

    I agree with Sue – they look more like vine weevil to me and they’re notorious here in the UK for the damage they do to the roots of plants, especially potted ones. Not sure of you have them down under though?

    There is a nematode treatment for them too. Autumn’s a good time to use it as it means the grubs don’t feed on your precious plants over winter. Squishing works well too and they really do need to be got rid of ASAP before they migrate off Scoop and into another pot.

    • Liz says:

      As suggested I removed them off Scoop and put them near some blackbirds who will no doubt be very grateful. They don’t seem to move much, I’m wondering how much they would migrate? I need to set up a video camera and observe one – that way I’d know if it was safe to just ex[pose them and leave them for the birds or if I need to actively intervene and kill them. I do struggle with the later so would be far happier letting nature take its course.

  9. Lilian says:

    We call them white curl grubs – scarab beetle larvae. I find them in the vegetable patch sometimes and other times yes in my potted plants. The chooks love them! Too bad you haven’t got any to feed them to.

  10. Andrea V says:

    Do they make for good bush Tucker (*wink*)?

    • Liz says:

      As much as I probably need a bit more protein in my diet I don’t think I’ll try and find out. I don’t imagine they are poisonous though.

  11. Jo says:

    Yuck. Glad you caught them in the mint before they moved on to something a little more precious.

  12. L says:

    I hate those things! I think there are quite a number of different beetles that have larvae like this, so the actual culprit will depend on the size of the grubs (the beetle will be similar to the size of the grub) and what types of beetles you have in your area. I believe that you can drown them easily just by sitting the pot in a bucket of water. Works well for small pots, but annoying for larger ones.

    • Liz says:

      Ah I like the drowning idea – sounds good. I am very tempted to hatch a couple to see what they become. Mr 2 would be very pleased with that idea no doubt.

  13. Louise says:

    Bummer for your mint, but what a crop of grubs! Never seen so many in one place before. I too have them, but never seem them like this! Mine are in my garden patch, ‘here and there’. I leave them be but I dont have them in plague proportions. I dont know what they are but there seems to be a consensus.

    I too have worried about eradicating them lest they be Christmas beetles which I love. And in any case in ‘here and there proportions’ they are manageable and part of your biodiversity? I have never found then a threat so I have left them be… Not very helpful am I?

    My philsophy is , unless it is a complete disaster leave it where it is and dont kill it, it might turn into a garden friend. But in your case for your mint it has been a complete disaster….bush tucker or chook food.

    • Liz says:

      I’ve found them for years too and this is the first time they’ve done any actual damage. Must have been one very productive beetle to lay all those eggs. My son and I plan to try and grow some into beetles to find out what they are (or at least what this lot are).

  14. Diana says:

    I occasionally found them as well not just in pots but soil. Last year I was wondering why many of our potato plant died early in winter and I found these guys in the soil where I planted potato. Found a few of them as well when I dig out sweet potatoes.

    • Liz says:

      I find them quite regularly in the raised beds but never many – I think the birds probably eat quite a few. Annoying that they are the potato.

  15. I had tons of these grubs in one container too. Fortunately, I had nothing planted in it. After this discovery, I went through all my containers (well, most) and found them in a couple of other containers. But not as many as this pot! Wow. And I though mint was invincible!

    • Liz says:

      I have no idea why they chose that particular pot – I have found many in any of the others. Perhaps a very fertile beetle.

  16. Maria (The Inner Gardener) says:

    Hi Liz

    I have recently posted a short article on my blog about using biological controls for problems with black vine weevil. I ordered the natural predators (nematodes) on line and applied them to a client’s garden, and hopefully they will attack the larvae undergreoung too. You can also buy nematodes that will control lawn grub – all safe as these predators usually occur naturally. Visit http://www.ecogrow.com.au for more infor on identifying the pest and the controls available.

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