I have a Yuka plant that has become infested with a white mark on the leaves which appears to start right back at the leaf base. The marks are egg like in shape and about half a centre metre diameter, so somewhat larger than some of the discussions we have found on this board which seem to describe a white powder like problem. I am unsure whether its an egg or some kind of fungus and what to do about it. The Yukka is in a dry room and seems quite dry Temperatures are around 20C most of the time. Some of the leaves are growing brown where they have been affected by these eggs/fungus.
Your Dracaena marginata has scale infestation. Safer insecticidal soap reapplied per label directions may cure it.
