Mysterious pest/fungus moving through my collection?

[Dollythehun]

Tindo, I don't agree that fungus does not leave webbing. Some fungus leaves filaments, as you know. In my 1st assessment, I saw "granules," and immediately thought of Southern Blight, of which those are a sign. After looking at this picture way to many times, I think I would agree with your assessments. Primarily because this plant was never in the ground and, I have had hitchhiker's hatch long after the plants came in.

[Tindomul]

Fungs filaments are different I think. I can't say I've seen it all. But when I think of Fungus filaments I think mycelia, bread moldy type looking stuff, more root like than insect web like. Insect webbing is more silky and fuller.
But I can see your point Dolly, thank you, I can see how a fungus might look like webbing.

[Dollythehun]

Thank you, Tindo. You are a very gracious man.

[ramonypony]

Hey y'all, somehow I missed seeing all these replies but I've returned with some news... I just found a perpetrator hiding in an oncidium's new growth. Yep- it's caterpillars!

[estación seca]

Show the photos to somebody at the ag or entomology department at the closest university. They will be able to tell you whether it's something local or an invader.

[Orchid Whisperer]

Caterpillar-like larvae indicate either a butterfly or moth adult, or a sawfly. Sawflies have 'prolegs' on nearly every body segment.

Caterpillar of moths and butterflies have prolegs on fewer body segments.

All three types of insects are potential plant eaters.

[Tindomul]

Originally Posted by Orchid Whisperer

Caterpillar-like larvae indicate either a butterfly or moth adult, or a sawfly. Sawflies have 'prolegs' on nearly every body segment.

Caterpillar of moths and butterflies have prolegs on fewer body segments.

All three types of insects are potential plant eaters.

Thank you, I had no idea how to tell them apart. I found a sawfly once and had to be told it was a not a caterpillar, and no one told me how to know that. You just never know when or how you will get the info you are looking for.

[bil]

Deffo caterpillar damage.

You can spray with a systemic insecticide, but be warned, not all caterpillars will die. It pays to run a regular eye over orchids that have been outside. Do it with a pair of forceps to hand, as when disturbed, the caterpillars will drop out of the leaf and escape, and if you use your fingers, you might miss and they will escape.
Very often they are hard to spot, as they use the silk to glue two leaves together.

In short any silk on an orchid should be investigated thoroughly.