Green powdery mold/algae growth on Oncidium roots and leaves

[shiba_ennui]

Hi! I just noticed some strange green growth on my Oncidium Aka Baby roots and leaves. It looks almost powdery and is green. It might be algae, but most pictures of algae on orchids I’ve seen are only on the roots and are darker in color. In addition, some of the roots look black ish but aren’t squishy like in a case of root rot. Any ideas on what this is and if it’s benign or not?

[Roberta]

It looks like algae to me. Quite harmless. What you see on the leaves might be encouraged by high humidity. What are your conditions? (Light, temperature, humidity)

[shiba_ennui]

I just got this plant 5 days ago. I grow them in an East facing window and supplement with an LED grow light hanging a few inches above. The temps are 75 degrees F during the day and drop to 65-68 at night. The humidity is 50-70%. Will the growth overtake my plant if I just leave it be?

[Roberta]

I think just leave it be. Algae won't overtake the plant. Conditions sound good. These do like to stay on the damp side, so the sphagnum medium is probably fine as long as it is reasonably fresh (holding moisture but also admitting air). If it is very compacted a repot could be beneficial, but unless there is a serious issue it is best to wait for new growth before repotting.

[Shadeflower]

I also think that is just algae. The newest bulb is looking healthy and plump so it's only the older bulbs that have algae on them. It probably just shows that the person who grew these was using an overhead sprinkler to water them.

I wouldn't worry about a few black spots on roots. In time it will grow new roots. It looks in good enough shape, I wouldn't worry about a few spots here or there, just observe them to make sure they don't spread.