Could be fusarium wilt on a oncidium?
 

Hi everyone! Now I would like to show/ask about a plant they gave me as a gift last weekend; Ive read somewhere that when you make a cut in a plant section and find a red/maroon ring around the cross section you made, Its one of the symptoms for fusarium wilt, the plant they gave me was relatively big and, and Ive found various sections like the one pictured. So its posible that all the plant is infected? any advice about it?... its a oncidium stenoglossum, at 1250m in the tropics

That looks like fusarium to me
There's a good image at this link
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There is more info here
Orchid Diseases

I've never taken a chance with this, and discard infected plants and their pots. Sanitize any cutting or other tools you used on this plant.

A healthy wild-collected plant will probably not have Fusarium. A lot of Oncidium type plants have this kind of coloring just below the surface of the rhizome. The classic purple photos are usually of Cattleyas. I would not cut up healthy plants looking for trouble.