Blight on a plant base made of lava rock?

Question

I received a very unusual Hawaiian plant from my husband that grows out of a lava rock. You can either plant the lava rock in soil or leave as is. I chose to leave as is, but there is mold all over the lava rock. If I take a fungicide for plants to it with an old toothbrush, will that get rid of it? And which fungicide do I use for best results? Once I get rid of it, I will plant it in soil, so I do not experience this again.

Answer 1

Are you sure it is mold and not moss?

If it is truly mold, a common plant fungicide should work, but you might try a moss and algae killer made from fatty acids. I would be very careful where you put either in relation to this plant, as there is a good chance that the products may be phyto toxic to the plant as well. You might try scrubbing it with the tooth brush and water first to see if that works.