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Black spot at dendrobium leaves.

#1 User is offline   Busy Ant 

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Posted 06 August 2016 - 11:09 PM

Hello there,

I have some dendrobiums that have some black spot at the leaves. I do not know whether they are chemical burn or insect bite. If anyone comes across this kind of problem, please advise me.

Thanks a lot.

http://i1159.photobu...zpsuokirtnx.jpg

http://i1159.photobu...zpsrm3gn5w7.jpg
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#2 User is offline   Phoebe 

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Posted 07 August 2016 - 03:34 PM

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This post has been edited by Phoebe: 27 October 2016 - 01:16 PM

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#3 User is offline   AhSeng 

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Posted 08 August 2016 - 09:22 AM

Yes, it is a common problem on dendrobiums. It is not chemical burn. It may be due to insect bite. It may be a bacteria/fungus problem and some spots is due to direct sunlight.
I thought I read that spots caused by bacteria look watery or slimey. It may be some kind of soft rot which is brown in colour.
I used to have a dendrobium that is fertilized using sheep manure pellets, this plant has lots of dots. Gave up on it. I suspect it is due to the sheep manure pellets. This fertilizer can make orchids grow well, unfortunately, it seems to cause spots. or it may be due to root damage. excess fertilizers and over-watering can cause root damage. The roots will look all brown and soft instead of white. When re-potting, can cut off all the brown roots, leaving the white ones. Sometimes I cut off all the roots.
Now I have one plant that has this problem too, and it is growing partly in soil.Someone gave me that.
Fungus cause spots too and is usually the case. Solution may be to provide air circulation by growing in a suitable environment. Don't water at night. evening 4-5pm probably can. Dendrobiums probably cannot be exposed to full sun, as many are grown under nettings. Sometimes showers and then the sun comes out may cause sun burn, although it is usually large patch of brown/gray/yellow on the leaves.
So in summary, make sure the roots are growing well, provide adequate air circulation.

This post has been edited by AhSeng: 08 August 2016 - 09:25 AM

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#4 User is offline   Yeong 

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Posted 10 August 2016 - 09:24 AM

Photo 1:
Likely to be snail bite. Water your plant at about 630pm, bring a torch light and shine it on the roots and leaves
at about 8pm, check for snail.

It looks like you have red spider mite problem, as I can see pits on the leaf. Use a magnifying glass to
check underneath the leaves, you may see red spider mite. Have you remove them? When was the last time you spray
insecticide on your plant?

Yor plant will not grow if it has red spider mites on it.

Photo 2 :
Due to virus infection, not serious, it won't affect the quality of the plant.
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#5 User is offline   Busy Ant 

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Posted 10 August 2016 - 07:51 PM

Hello all,

Thanks so much for your replies. I will try to follow your recommendations.

If I put dendrobiums by the window (indoor) with morning sunlight, will they grow & bloom ?

Thanks again.
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#6 User is offline   Busy Bee 

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Posted 11 August 2016 - 09:26 AM

Hi Busy Ant,
Whenever I see black/rotting spots on my orchid leaves, I would get a pair of sterilised scissors and snipped off the portion of infected leave. Sprinkle some cinnamon powder on the open wound.
Morning sunlight is always the best for dens.

Have fun! ^_^/>/>
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#7 User is offline   Busy Ant 

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Posted 12 August 2016 - 08:30 PM

Hello all,

Thanks alot for your replies.
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