White chalk-like fungus/substance on plants
I need help identifying a white chalk-like fungus or substance of some kind that consistently seems to plague certain plants that I grow in my house. As the attached photo shows, the two palm plants are the worst affected, and they can become almost completely covered if I don't wash this chalky white substance off every couple of weeks. It does not seem to harm the plants much, and it reproduces very fast. Some plants seem to be unaffected, but I can't tell whether it's because of their position or their species.
I have tried spraying with two different kinds of commercial Fungiside (Safer Brand and Garden Safe) but neither seemed to have any effect.
Can anyone help me identify what this substance is, and how I can get rid of it?