The Orchid Forum, for the UK and Europe (previously known as The UK Orchid Forum) • View topic - Cymbidium - white & yellow spots/pests on leaves
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PostPosted: Sat Mar 11, 2017 2:21 pm 
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Please help me identify and *treat this! I have four Cymbidiums and all, to varying degrees, are affected. This developed within 1-2 weeks, so is quite quick spreading.
These things are too small to say whether they're insects or fungus or what... They do not come off easy (tried to gently scrape them off with my fingernail - no luck, the suckers are well embedded).

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Image

Underside of the same leaf: Image

PLEASE HELP!!


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PostPosted: Sat Mar 11, 2017 3:08 pm 
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Hi,

This looks similar to the white scale insects on the attached link: https://www.google.co.uk/search?q=white ... g1Z6HDXQhM:

If I have any insect problem I tend to use Provado and I have just looked at the bottle but there is no mention about treating Scale insects, fortunately I have never had them but there are products on the market to treat it. As these are sap-suckers, it is likely they are also causing the marks on your leaves rather than it being a separate disease.

Maybe some-one else here with (unfortunate) experience of this can confirm the diagnosis and treatment ?

Steve


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PostPosted: Sat Mar 11, 2017 4:03 pm 
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This is one of the worst cases of scale i have ever seen and i doubt that it got as bad as that in a couple of weeks. It is more likely that it has gone unnoticed for months. You need an insecticide that will kill scale and you will need to do several applications over a few weeks. If the plant has plenty of foliage it may be best to remove some of the worst affected leaves or alternatively use some methylated spirit on a kitchen towel to wipe it off before spraying with the insecticide.

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PostPosted: Sun Mar 12, 2017 12:10 am 
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Thank you, Terry! It could have well gone unnoticed, you're right. I didn't do a thorough inspection when I watered them (should have done, as it is spring), so only noticed today...and of course now it's right-in-your-face obvious :-(.

The leaf pictured has been removed from the plant - I believe it may be the one that started the problem. It is the worst! affected one - I thought it would make the best specimen for the photo. The other leaves have fared a lot better than this one (was it just the tastiest one to these bugs?!). So hopefully, it won't be too difficult a job to rectify the problem... to be seen.


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PostPosted: Sun Mar 12, 2017 12:19 am 
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Imidacloprid/thiacloprid works well on these.
Bayer has some products available (Calypso, for ex)


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PostPosted: Wed Jun 07, 2017 7:00 pm 
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So... What happens after?!

The infestation is gone now, thankfully. All the orchids have been repotted, treated and cleaned... Two weeks and we're still bug free (fingers crossed).
However, what I have left now are leaves with blacks spots on them. Are these, essentially, 'bite marks'?! Or is this some sort of a fungal problem following the bug damage?

The spots are small, black coloured, mostly on the underside of the leaves. They seem to be more concentrated towards the tip of the leaf, rather than the base.

Please note, I have photographed one of the worst affected leaves (it does have a split down the centre, but I believe that's mechanical damage acquired by accident during reporting)


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PostPosted: Wed Jun 07, 2017 8:08 pm 
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Your best bet which will work wonders is to immerse the plant in a strong (and I mean strong ) solution of household bleach like Domestos.After leaving the plant in for 10mins or so and then give it the same treatment with fresh water. Make it strong enough to put a good lather on top of the container. Domestos will never harm your plants but will get rid of all the bugs.
Ed



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PostPosted: Wed Jun 07, 2017 8:13 pm 
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Strong bleach? Really? Doesn't that kill everything living, including the plants?!

Could you be a little more specific about the dosage/proportion please? Am I right understanding that you mean liquid/laundry bleach?

On very close inspection, there don't seem to be any more critters on them... just the black spots.

These plants have been through enough, I'd really hate to stress them further :-/


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PostPosted: Thu Jun 08, 2017 7:39 am 
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I blanched too when I read Ed's advice about using strong bleach! But Ed is an experienced grower and knows what he is talking about. I shall bear that advice in mind if I ever have such a bad infestation of bugs. Mind you I will only try it on a single plant first :lol:

As far as your plants are concerned I would watch and wait, particularly if you are showing one of the worst affected leaves. Many cyms, particularly with devonianum in the background are prone to leaf spotting and although it is unsightly it is no causee for concern.

On second thoughts I have a cym that was going onto the compost heap. I will try the bleach treatment and report back in a week or so.

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PostPosted: Thu Jun 08, 2017 11:46 am 
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elk4orchids wrote:
Strong bleach? Really? Doesn't that kill everything living, including the plants?!

Could you be a little more specific about the dosage/proportion please? Am I right understanding that you mean liquid/laundry bleach?

On very close inspection, there don't seem to be any more critters on them... just the black spots.

These plants have been through enough, I'd really hate to stress them further :-/

Hi. Just take a look on YouTube on Douentza Orchids and you will find all you need to know. I can only stress that bleach will definitely not harm your precious orchids. I wouldn't publish these things if I thought there would be any danger of destroying any plants.
Ed



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If you have any back bulbs have a good look round them and anywhere else the leaves are covering the bulbs. Check any house plants you have too...they also go for succulents.


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PostPosted: Fri Jun 09, 2017 1:08 am 
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Those videos are great. Thank you, Ed!


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PostPosted: Sat Jun 10, 2017 11:19 am 
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cricketerry wrote:
On second thoughts I have a cym that was going onto the compost heap. I will try the bleach treatment and report back in a week or so.

I'm aware some people recommend bleach as a treatment but I haven't seen enough data on the Internet to convince me that it is so commonly used that I would use it as a first choice treatment.
Like Terry, I would feel very uncomfortable about putting anything living into bleach, despite some having done so with no ill effects ! :shock:
But I've got an open mind and I'd also give it a go (but only on some rough old Noid at first), seeing as some of the purpose bought treatments just don't do as they say on the tin.

It'll be interesting to know how you get on with yours Terry, keep us informed ?

Steve


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PostPosted: Sat Jun 10, 2017 6:39 pm 
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Will do Steve. I dunked it this afternoon and will now wait to see what happens. This is the plant pre bleach soaking.


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PostPosted: Mon Jun 19, 2017 1:57 pm 
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Hi Terry,
How's that orchid doing now?


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PostPosted: Mon Jun 19, 2017 9:46 pm 
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Here is the plant following its 10 min chlorine bleach treatment. I have tried to show it in the same orientation as the 'before shot'. The foliage looks unharmed!


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PostPosted: Tue Jun 20, 2017 8:48 am 
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Funnily enough, just yesterday I was also thinking "Wonder how Terry's bleaching is getting on?", so thanks for the update, possibly still early days yet, watching this spot !
I wonder if you will see this plant (which was destined for the compost heap) in a different light now ?

Steve


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PostPosted: Tue Jul 18, 2017 3:31 pm 
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I hope your cymbidium is still alive Terry ?

Because I've just gone and done it, treated a couple of plants to the 'Domestos' treatment. :shock:
I Googled a few Posts about it then mixed 1 part bleach to 4 of water and used a mister to spray upper & lower of the leaves making sure they were thoroughly wetted.
The Aerangis articulata (attached) was the worse, small black spots over the leaves and where there was a larger black spot, the leaf would yellow (as can be seen in the photo). The spotting is worse under the leaves.
Its in spike too which is a shame but I'm thinking if the bleach treatment doesn't kill it, the spots would in time anyway. :(

Steve

Does anyone else grow this ?, of my collection, it is the slowest developing spike EVER, this spike started in November 2016 and still a way to go yet ! :yawn:


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PostPosted: Wed Jul 19, 2017 7:11 am 
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Steve did you wash the bleach off after spraying or did you just spray and leave it? Mine is still alive!

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PostPosted: Wed Jul 19, 2017 1:41 pm 
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Steve here is a pic taken today of my plant. As you can see new growths and roots all look fine so I will be quite happy to use Ed's method in future :D .
However this particular plant will not get a reprieve as I think it is virused and the safest place for it will be the bonfire!


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