Virus vs Fungus

[failingflopsis]

I am just sick. One of my favorite Dendrobiums (sorry it doesn't have a tag) has developed these spots. They start with a few black dots on a leaf. Within days the leaf turns yellow/brown and falls off. I am hoping that there is a cure before the whole plant collapses. Any ideas on cause? Is there a cure? Thanks in advance for any help. The first two photos are of the Dendrobium the last is a Cattleya which is starting to have the same (maybe?) problem.

[King_of_orchid_growing:)]

How cold has it been?

How are the roots?

Are the leaves dying back on old canes (Den)/pseudobulbs (Catts)?

How big are the pots.

How often do you water?

Do you mist the leaves?

[musicloveranthony]

sunburn?

[failingflopsis]

Originally Posted by King_of_orchid_growing:)

How cold has it been?

How are the roots?

Are the leaves dying back on old canes (Den)/pseudobulbs (Catts)?

How big are the pots.

How often do you water?

Do you mist the leaves?

We have had a very nice summer. Daytime temps in the sunroom are around 80 going down to 65 at night.

The roots through the clear plastic pots look great. The Den is spiking right now.

4" pots for both.

I water them every 5 to 7 days depending on whether it has been sunny or cloudy by running water through them. My collection is small enough that I don't need to use a sprayer to water so the leaves rarely get water on them.

I don't mist them.

[Ray]

Looks to me to be a fungal problem. That third image shows a classic "water left standing as the cool of night approaches" issue, but don't forget that insects piecing the leaves also are a great vector.

[zxyqu]

Well just a quick thought, though I have no idea on what it is. I hope you have quarantined these orchids, since you last photo shows the Catt still with other's nearby. You definitely want to separate them, less risk them all getting the infection.

[failingflopsis]

Originally Posted by zxyqu

Well just a quick thought, though I have no idea on what it is. I hope you have quarantined these orchids, since you last photo shows the Catt still with other's nearby. You definitely want to separate them, less risk them all getting the infection.

I have heard the idea of isolation used before but don't quite understand what it means. Is it enough to move them a few feet away or should they go to another room? Can all the "infected" orchids stay together or should they each be separated? Thank you all for your help, I really appreciate it.

[zxyqu]

I'm not an expert on this, and without knowing the nature of the pathogen, it's hard to say if it can jump from plant to plant, or likely needs to come in contact with a damaged plant. I move them to a new room, that I keep suspect orchids in, especially until I figure out what is going on. My thoughts are merely that I'd rather it not spread regardless of the likelihood of it jumping to another plant. The reason I mentioned it here, is because from the picture, it has seemed to spread to another orchid. Better safe than sorry.

[Des]

I would place a sticky pad in amongst your plants and see what you catch. I have known thrips to have this affect on some plants The male mosquito can also cause this sort of damage to plants . When I am unsure of what is chewing on my plants I use my "Whiz-bang" it is my mixture of systemic insecticide and fungicide And I repeat two weeks after the first application think I can see some chloroesys in the catt leaf so check your fertilizer,the problem could also be due to too much or too little of something

[failingflopsis]

chloroesys?? Whoa, you lost me on that one. I use MSU fertilizer, weakly weekly.