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Basil Problems - Dying Leaves and Little Black Insects

Hi all

I have four indoor basil plants which I've had since the summer.  I've got a couple of problems with them, which could well be totally unrelated.  

The first is that every now and then a stalk of three seems to give up and all the leaves on it curl up and die.  Some leaves are also getting discoloured.  Here are some photos:

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The second problem is little black flying insects.  I don't know if they are actually causing a problem, but they certainly seem to like hanging about the basil plants.  Are they problematic or a sign of a problem?  Again, some photos:

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Huge thanks :)

Max

Posts

  • Pete.8Pete.8 Posts: 11,287

    They look like Fungus Gnats Max.

    Thee young grubs live off dead vegetation in the potting compost, so remove all dead bits and dead/dying leaves.
    A good topping of grit in the pots will deter them.
    I think your main problem is the time of year with such weak sun and not much daylight, the plants are struggling to grow and any infestation will weaken them further.

    If you have a magnifying glass, have a look on the underside of one of the affected leaves and see if there are any bugs.

    Last edited: 06 January 2017 11:44:24


    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • Hi Pete

    My apologies - I forgot to get back to you to say thank you.  

    I looked up images of fungus gnats and they do indeed look exactly the same.  I'm wondering if I might have over watered at some point (could that account for the gnats AND the unhappy leaves?)

    I've given the plants a good clean up, removed the dodgy bits, etc.  Will see how it goes...  

    I do have a couple of other questions.

    1.  How long should I expect an indoor basil plant to live?

    2. Should I be feeding them and if so what would anyone recommend?  I'm not currently feeding.

    Oh, and one last thing, someone on another forum mentioned fusarium wilt.  Do you think there's a chance it could be that?

    Many thanks

    Max

    Last edited: 16 January 2017 18:27:30

  • When I zoom in on the dead sections I see some webbing which leads me to believe you have an infestation of spider mite which also matches with the damage visible on the sickly-looking leaves.  You'll need a magnifying glass to see them.  Only cure (on edible crops) is predator mites but they are very expensive and probably hard to get at this time of the year.  Personally I would dump the plant and start again - basil is only short lived and I've never managed to keep one going for more than a year.

    Last edited: 16 January 2017 18:44:00

    A trowel in the hand is worth a thousand lost under a bush.
  • Pete.8Pete.8 Posts: 11,287

    Hi Max - you're welcome.

    Bear in mind that Basil originates from Thailand - not the Med. So we're trying as best we can to imitate the tropical environment that it comes from, and mid-winter in the UK is going to be a struggle for it.
    The plant would like very warm, humid conditions with about 12 hours of strong light every day - and it's not going to get that here at the moment.

    Indoor basil will lasts as long as it looks edible - a few months realistically if you're lucky. Sow just a few seeds every month from summer and you'll be good for a winter/spring supply. Once they have a few sets of leaves, pinch the top out to get a bushy plant.

    All plants are driven by light, only light allows them to use the feed we give them. With little decent light this time of year just an extremely dilute feed now and then and let the compost almost dry out before watering again. Use a fertiliser not designed for flowers as it's leaves you're after.

    Fusarium wilt is quite possible. Your plant doesn't look in the best of health for the reasons above leaving it weak and open to infection.

    I sow basil in a propagator in March and get masses of the stuff by mid-summer. I don't bother after that as I've usually ended-up with plants that look rather like yours :)

    Best of luck
    Pete


    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • Hi all

    I thought I’d write back with an update….  After giving the plants a good trim and removing the dead leaves etc from the top of the compost, the gnats seem to have disappeared.  So thank you for that tip :)

    The plant photographed above is still going but not looking great.  I should have mentioned however that this was the worst of my basil plants.  Here’s a photo of the one which is doing the best out of the few that I have.  It was grown from a cutting in the summer (probably around July time at a guess).  Not brilliant, but not bad considering our thermostat rarely goes above 15C! 

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    In terms of a topping for the compost, could I use pistachio shells? 

    Thanks for all the help

    Max

    Last edited: 30 January 2017 18:07:02

  • Pete.8Pete.8 Posts: 11,287

    You're doing really well with that Max - credit to you.

    As for pistachio shells - I imagine they would be ok, but not in my area of expertise..

    Pete


    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • Thanks for the kind words Pete8!  Very encouraging and warming :)

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