How do I treat for plant scales?

Scales is not a condition of blight or fungus, it is an insect problem. Underneath that scale is a small mite. The best way to get rid of these mites is to cover each 'scale' with a product called Neem Oil. It can be purchased at many garden supply stores or places such as Tractor Supply. Once the scale is covered with this oil it suffocates the mite, and your problem is solved. Make sure to cover each one of them. And only use in the cooler parts of the day to avoid burning the plant.
 
severe case of plant sales
 
Each chalky-looking spot is a scale. These are so close together that they are nearly indistinguishable. This plant is so heavily covered that it will not be salvageable. It will have to be removed.