Fusarium Purple Ring - Useful Diagnostic or Myth?

[nhbeek]

So I had a problem oncidium that was in declining health with rotting backbulbs and dying new growths. I decided to try and cut off a healthy lead and lo and behold there was a bright purple ring in the rhizome.

That plant is now gone since it was clearly diseased with something. The problem is that after dealing with that I noticed some of its neighboring cattleyas had dying back bulbs. That isn't too concerning generally speaking, but I cut into the rhizome near those backbulbs and, well there is a purple ring.

So is the purple ring an actual diagnostic symptom or is that BS?

[Dimples]

It's bs. Fusarium isn't nearly as common as random sources on the internet would lead you to believe, but people on the internet latch onto things they read/hear and run with it regardless of the validity of what they're saying.

I just did a quick google search for info about fusarium in orchids from .edu sources and not a single scientific paper (quickly looked at 3) mentioned a purple ring in the plant tissues as a diagnostic tool or symptom.