I have a definite case in the greenhouse; could just about see the moving red dots on the underside of my (still cropping) cucumbers' leaves. I've never had them before, and as I thought they preferred hot dry conditions am slightly mystified/peeved.
Have picked off all obviously infected leaves and sprayed with vitax 2-in-1 which is an organic oil-based product claiming to kill them and their eggs. But I don't imagine I will by any means have got all the little b*****s.
Now, what shall I do about the winter? I normally keep the greenhouse frost-free with tender plants, and some winter crops: lettuce, chard, kale, etc. I've got a few precious plants I can't leave out like a good sized lemon tree, so there isn't the option of letting the frost penetrate to kill off nasties.
Will the RSM over-winter and be back next year? I think I can't use a biological control now as the nights are too cold? Can I fumigate in any way to get rid of them?
Thanks for advice.
Yes..it will over winter..it may not be active and there might not be much evidence it's presence over winter..but as and when spring comes and temps start rising again they'll start doing their thing again.
I've got permanent things growing in my GH...like peach etc. and once you got it it take quite doing get rid of RSM...I'm not bothering to try..I can keep it under control so the number do not get too big and other than plants looking bit under weather..no harm done.
I would not worry about your winter crops..RSM will not have much effect on those..if any..your GH will still be on cool side for them to properly multiply..and once you clear them out next spring..problem sorted..and maybe then give your GH good clean/spray..something like Armillatox..sorts any algae in same time too ;)
One temperary 'control measure' comes to mind...once you remove obvious things like effected plant material...you could give the whole GH thorough wetting..just water..drench it..but wait cooler weather first..they don't like cold and damp..
Quote from: Morris on October 13, 2010, 14:42:44
I have a definite case in the greenhouse; could just about see the moving red dots on the underside of my (still cropping) cucumbers' leaves.
How did you see them?
You may be able to recognise a colony and see the minute amount of shuffling that goes on - but many people just see a few red things roaming with the naked eye - which means they aren't spider mites! anything really tiny that moves clearly and fast enough to see isn't a vegetarian - it will be a predator.
You need a very strong magnifier to see them move individually (a jeweller's loupe or equivalent) and even then you need some patience to see them move - a second or more to cover their own body length.
Red spider aren't red either. They are buff mostly, sometimes tan, rarely get to orange. The predator Phytoseiulus persimilis is a much clearer orange.
If you do get the predator in next spring then don't go overboard with cleaning the following winter - a) they are pretty efficient killers and b) it's worth giving them a chance to overwinter themselves.
Cheers.
I used a x 10 magnifying glass to confirm. ;D
But I could make them out with my naked eye; just. There was also little webbing. They were pale orange.
Sounds like you've got the 'real deal' ::)...unfortunately...If it is just appeared first time..it might be that once you clear affected plant you might get rid of the problem..might..
Unfortunately those predatory ones are not as hardy as the RSM...and they need intoducing into greenhouse once temperatures rise..early summer..I use them every year with sort of success..they don't get rid of the problem but keep situation under control..if introduced early enough and RSM is not take over yet...