What is this weird texture under oncidium leaf?
 

I discovered this strange, raised, rough texture under an oncidium leaf. What is causing this? I’m thinking it’s some kind of pest. Input would be appreciated. Thanks

Hard to see in your photo. Can you scratch these lumps off with a finger tail? If so, it could be scale insects.

If the lumps seem part of the leaf, these could be a reaction to sap sucking insects, but are more likely caused by oedema. Oedema occurs when the water pressure in the leaf cells is too great, causing them to burst and leading to the bumps/blisters. This physiological disorder is usually caused when roots are wet and warmer than the leaves, which leads to the plant taking up water faster than it can lose it through transpiration. It's more frequent in late winter/early spring, as the days will often be warmer but nights still cool. Oedema is a purely cosmetic issue and has no negative effect on the plant (unless entire leaves are covered in blisters).

You cannot scratch it off. It is part of the leaf. I will keep an eye on it. Thanks Camille!