Fungus? Virus? Bacteria?

[Connie Star]

I'm visiting a dear friend in Costa Rica. One of Margaritas orchids appears to have a bad infection with something, I'm not sure what. They have had a very rainy (3 times normal) season.
Any ideas what this is (and what the orchid is)? It appears to be doing surprisingly well considering.

[RobS]

Could be a Rossioglossum schlieperianum which is native in Costa Rica. Definatly something from the genus or a hybrid.

IOSPE PHOTOS

On the disease I'd say bacterium so try to keep the affected parts of the plant dry.

[BikerDoc5968]

While I'm certainly not even close to knowing much of the Oncidium Alliance plants, I have read that many naturally get black spots on the leaves. I understand the concern especially with all the rain, but it sure looks healthy from the pictures. If it is available (probably not), maybe a spray of SA-20/Physan-20 or if you can find some Copper Sulfate at a big box store; this is the active component in Phyton-27 (21% Copper Sulphate Pentahydrate) that is so costly and you can purchase the granules for about $8 and mix gallons of the stuff! Most CuSO4 is hydrated, i.e., contains some water. The most common form is the pentahydrate salt. Its specific gravity is 2.284. From this you can calculate how much to add to a gallon of water to produce a 21% solution ( water has a sp gr of 1 for all practical purposes).