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Spider mite in greenhouse

McRazzMcRazz Posts: 440
in Problem solving
Hi all,

Last year i had a really bad spider mite infestation in my greenhouse. By the time i'd learnt what i was looking at it was too late and they had managed to totally wipe out my cucs and aubergines which made an already poor summer here in the SE even worse.

I adopted the classic insecticide, soapy water, squishing, neem oil approaches but none seemed particularly effective with an infestation that was already far advanced.

Anyway, fast forward to 2022 and i've noticed one or two on my 'over winter' greenhouse plants so i want to do a pre-emptive strike on them prior to this years veg crops being planted.

I would like to fumigate if possible followed by a deep clean, however i have a splendid colony of NavelWort and Soleirolia which i am keen to protect.

Appreciate fumigation isn't the done thing these days but its an old structure that came with my property and i feel a drastic reset is required before i adopt a more holistic approach.

For info the greenhouse is about 4 x 3m, autovent roof openers, solar fan ventilation and i remove four corner glass panels every summer, so i don't think stagnation is the issue although i am looking to add more solar ventilation this spring.

Any advice/anecdotes on effective plant friendly products and associated techniques would be very welcome.

Thanks in advance!


Posts

  • Pete.8Pete.8 Posts: 11,340
    If your greenhouse is made of aluminium I think the sulphur in the fumigation bombs may damage the aluminium.
    I'm not entirely sure about that, but worth checking first.

    Spider mite isn't something I've had to deal with, but I understand that neem oil can be a big help.
    It doesn't actually kill them with a toxin, it just glues them in place so they die. It's something you'd need to use frequently to have an effect. So you may need to use it more often than you did before.

    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • Cottage CompostCottage Compost Posts: 496
    I can't offer much help but I am very interested to know how you get on. I had them on some gardenias last year and really did struggle to get rid of them. I ended up completely submerging the entire pot and plant in cold water for two days before I won. You can't this with your greenhouse obviously. 

  • DaveGreigDaveGreig Posts: 189
    Red spider mite don’t like humidity so keep the greenhouse floor wet. They really don’t thrive in damp conditions. There’s also biological control for sale online that’s effective. None of these measures will completely eradicate the problem but in my experience they will reduce it to a manageable level. There’s no need to resort to chemical control which in my experience can be a bit hit or miss and it kills all the real spiders and we want them.
  • McRazzMcRazz Posts: 440
    Pete.8 said:
    If your greenhouse is made of aluminium I think the sulphur in the fumigation bombs may damage the aluminium.
    I'm not entirely sure about that, but worth checking first.

    Spider mite isn't something I've had to deal with, but I understand that neem oil can be a big help.
    It doesn't actually kill them with a toxin, it just glues them in place so they die. It's something you'd need to use frequently to have an effect. So you may need to use it more often than you did before.

    Hi Pete, thanks for your advice.

    I actually bought a sulphur candle last year but i'm quite reluctant to use it due to the incidental plants that exist within the greenhouse and contribute to its overall environment. The fact it may stain/corrode or damage my frame just reinforces my resolve to not use it.

    I had heard there were other smoke cones but a quick check of Amazon comes up with very hit and miss reviews.


  • McRazzMcRazz Posts: 440
    Cottage Compost said:
    I can't offer much help but I am very interested to know how you get on. I had them on some gardenias last year and really did struggle to get rid of them. I ended up completely submerging the entire pot and plant in cold water for two days before I won. You can't this with your greenhouse obviously. 


    They're insidious little blighters for sure.

    I actually work in horticulture (mainly construction) and have been a keen gardener for nearly 20 years but this is the first time they've ever become an issue for me.

    Regardless what happens i'll be sure to update this thread with my solution...or continued struggles...
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