Black Spots on Orchid Petals and Roots: Fungus, Scale, and Humidity Issues

Question:

Hello—I'm really worried about my orchid, a beautiful green and purple speckled one from my mom for Mother's Day. I put it on top of our fish tank for humidity, but now the petals have black moldy-looking tips and black speckles on the roots (like pepper). The stems have little brownish-orange bead-like things. It was blooming with many buds, but they're falling off unopened. HELP PLEASE!!!

Answer:

Hello Ashley,

The black mold on petals sounds like Botrytis fungus from constant fish-tank humidity—moisture on petals overnight in dark, humid conditions is a prime breeding ground. It may also be on exposed roots. The brownish-orange beads could be scale insects, which slowly kill orchids if allowed to multiply. Unopened buds dropping is likely related to the fungus.

To save remaining buds:

1. Move the orchid away from the fish tank immediately.
2. Check entire plant for black mold; clean with isopropyl alcohol and soft cloth/tissue (or mild dish soap and water). If mold has been there days, it may leave gray/black marks.
3. For scale: use isopropyl alcohol on cloth, wipe leaves top and bottom from base to tip. Check cloth for removed spots. Unfortunately, visible scale means more lurk in the pot. Full eradication requires repotting in fresh media, cleaning all roots.

Hope this helps.

Jim Kawasaki
San Jose, CA