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Small dark Grey Caterpillars on My Mustard

I have a bed with Green Manure Mustard in it which will die off in the Autumn and enrich the soil so I am not worried about its ultimate fate.

The plants are about 3 foot tall and have bright yellow flowering stems

There are 1/2 inch long dark grey caterpillars with a black stripe down each side all over them eating the plants from the top presumably where the smallest and juiciest bits are

? Anyone know what they are please
I dont possess an I Phone 
Everyone is just trying to be Happy.....So lets help Them.


  • DovefromaboveDovefromabove Posts: 86,108
    Hard to say without a photo but as mustard is a brassca perhaps they're Cabbage Whites?

    I'd cut the mustard down before it forms seeds or you'll have mustard there next year as well, and the following year, and the year after that, ad infinitum  :)

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

  • wild edgeswild edges Posts: 9,927
    Do these caterpillars of grey poop on mustard?

    Very tenuous joke sorry :#

    If there's loads of them and they're small then I'd suspect a sawfly larvae rather than a moth or butterfly caterpillar. Possibly turnip sawfly? There is a specific mustard sawfly but I don't think we get them in the UK.
    Tradition is just peer pressure from dead people
  • NewBoy2NewBoy2 Posts: 1,813
    I have checked out Mustard sawfly and turnip sawfly and they look like what I have.

    I realise that all insects have a right to exist but do we consider them helpful or damaging for our vegs

    Everyone is just trying to be Happy.....So lets help Them.
  • BobTheGardenerBobTheGardener Posts: 11,391
    In general, sawflies are bad for plants as they tend to quickly defoliate them.  Trying to encourage their natural predators is probably the most nature-friendly way to go.  Most small birds will feed their chicks on them so hanging bird feeders on any trees or large shrubs (birds won't come unless there's some cover to escape into) near your crops will help with all types of insects considered pests on veg.  If that's not an option then spending a few minutes picking them off by hand works wonders.  ;)
    A trowel in the hand is worth a thousand lost under a bush.
  • NewBoy2NewBoy2 Posts: 1,813
    The mustard is in the middle of an allotment plot. I have knocked them off every day but i think a plastic box and picking them off is necessary tomorrow.

    Thanks BOb
    Everyone is just trying to be Happy.....So lets help Them.
  • wild edgeswild edges Posts: 9,927
    I put them on the bird table after I've removed them by hand. They're always popular.
    Tradition is just peer pressure from dead people
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