Orchid virus? Pest? Help!

[fenderfemme]

Hi,

I've recently bought three new orchids, a zygopetalum and two Cambria.
(Colmanara Masai Red & Miltonidium Bartley Schwarz).


My Zygopetalum is doing fine, it's finished flowering and is having a bit of a rest.


The two cambrias are still flowering but have developed black spots on their leaves. It originally started on the Colmanara but has recently appeared on the Miltonidium.

My thoughts are it's either a virus or spider mites, I haven't seen any mites on the plant though.
I can only upload one photo for some reason.
Can anyone help??

I don't want to lose them

[fenderfemme]

I'm thinking it might be 'bacterial brown spot'?

Hoping it's not a virus

[euplusia]

Mites are nearly invisible. Best is to rub the underside over a (black) paper sheet and then use a magnifying lens.

[gravotrope]

Not a virus from what I can tell, but it will never go away. They could be mite bites that fungus or bacteria got into. Treat plants for fungus/bacteria. My Colmanara looked worse but continued growing, I didn't want to keep cutting leaves off of it so I left them and occasionally spray with 1 tab uncoated aspirin per gallon (3.78L) to keep it from spreading to the new growth which looks much better.

[fenderfemme]

I've read that some orchids do tend to get 'freckling' on the leaves so I ignored the marks when I bought it, thinking it was normal.

It's a lot warmer in my house than at work (I work in the garden centre) so I think the increased heat & misting has bought on the bacteria!

Annoying because it's spread to my other orchids :/

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[gravotrope]

Welcome to the board!

Yes it is normal to an extent (especially in greenhouse plants), but it can also be reduced on future growth. If you're going to use uncoated aspirin, just make sure you don't use it on any plant that's in spike (it would halt the growth until you resume a regular watering/fertilizing schedule.)

[Orchid Whisperer]

Probably Phyllosticta leaf spot (Guignardia), a fungal disease. see:
Orchid Diseases

Not all fungicides will treat every fungus, use one that will work with the particular problem you have:
http://www.staugorchidsociety.org/PD...idDiseases.pdf
NEEM is relatively safe, easily available and will work on this fungus, use per the directions on the container.

Good luck

[tucker85]

It's not a virus. I agree with the others that it looks like a leaf spotting fungus. That type of fungus doesn't kill orchids but it looks unsightly and it can spread. You can reduce the spreading with good air circulation, keep some space between plants and don't wet the leaves in the evening. Also using a fertilizer that contains calcium and magnesium will help build stronger leaves that resist fungus. If your fertilizer doesn't contain calcium, use a calcium/magnesium supplement a couple times a month during the growing season.

To check for spider mites, wipe the underside of the leaves with a damp, white paper towel. If you see tiny red dots on the towel, then you have spider mites.