Black Spots on Philodendron Xanadu: Harmless or Scale Insects?

Question

black spots Hello, recently purchased a philodendron xanadu with black spots on underside of some leaves, plus faint yellow spots. Plant looks healthy otherwise. Black spots wipe off with water. Concerned? Mostly on leaves around base. Can I cut those stems? Also, bluish/white film on top of almost every leaf when brought home—looked like water spots. Wiped each leaf with damp cloth. Advice appreciated! Marie

Answer

Hi Marie, if dark spots rinse off with plain water, nothing to worry about. However, if spots return slightly raised with hard outer covering requiring pressure/scraping to remove, they're scale insects needing treatment. I'll wait for your confirmation before posting treatment info.

Bluish film was likely residue from pesticidal/fungicidal sprays nurseries routinely use. Yellow spots not concerning if limited to older leaves.

I've written an article on plant pests and treatment I'll email free to anyone requesting at wcreed@HorticulturalHelp.com.

Will Creed, Interior Landscaper
Horticultural Help, NYC