pseudobulbs that rot

[sunny]

i had a chia lin that is rotting right through from the pseudobulb where it meets the roots. the bulb turned black and then separated at the joint of the bulb and the root. it happened very quickly. when i unpotted the plant to check it, the roots were dead and had obviously died first.
i treated it with physan 20 twice when i first saw it and isolated it.

what is this? how much trouble is my greenhouse in? this was this week.

[Ray]

"Black rot" in cattleyas is typically caused by one or both of the fungi Pythium ultimum and Phytophthora cactorum. It is systemic, so a topical treatment such as Physan is useless in controlling it.

It's also too late to use a systemic on that p'bulb, so the appropriate course of action is to remove anything having a trace of black in it and dust the wound with cinnamon.

[Doc G]

To be even safer, remove the plant from the pot, remove as much media as possible, treat with a fungicide, with a clean tool trim back into healthy growth, treat the wound and repot in a clean pot.

[sunny]

i thank you for your response, but it is gone. i got the plant in costa rica in march and it didn't last long. i do not know how to tell the difference between a virus and fungus. can you help? do both spread to other plants?

carol

[Ray]

There are fungal-, bacterial- and viral pathogens that affect plants, and they all can be spread from one to another, especially via water (splashing, dunking in same tub) or through injuries that allow internal liquids to spread to other plants.

Fungal and bacterial ones tend to display as "rots", while viruses do not. More often than not, they are characterized by color break in the flowers, some leaf surface discoloration, and often, no outward signs at all, just a lack of vigor.

Do a Google search for "orchid disease" and you'll learn a lot.