Question
I have one boxwood, out of many, that has developed white raised spots on the stems. You can scratch them off with your nail. I can't tell if it is a fungus or some other disease. It started with just a few spots but has rapidly progressed and now some of the leaves are falling off. I have looked on the web for answers, but have not been very successful. Thanks in advance for your help.
Marsha

Answer
Sounds like one of the scale insects. These are insets that live their live under a shell like structure. They have sucking mouth parts and suck the plant juices from the shrub.
When plants are heavily infested with scales, leaves may look wilted, turn yellow, and drop prematurely. Scales sometimes curl leaves or cause deformed blemishes or discolored halos in fruit, leaves, or twigs. Bark infested with armored scales may crack and exude gum. Certain armored scales also feed on fruit, but this damage is often just aesthetic. Soft scales infest leaves and twigs but rarely feed on fruit. A major concern with soft scales is their excretion of abundant honeydew, which contaminates fruit, leaves, and surfaces beneath plants. Honeydew encourages the growth of black sooty mold and attracts ants, which in turn protect scales from natural enemies.

I would recommend that you treat the shrubs with a systemic insecticide that will kill the scales.

Systemic insecticides are absorbed and moved within plants. If the plant is infested with a scale species susceptible to systemic insecticide, systemics are particularly useful where it is not practical to spray because plants are large or spray may drift to unintended areas. Depending on the product, systemic insecticide may be applied by spraying foliage, injection or implantation into trunk vascular tissue, or applying on or into soil beneath trees and shrubs, where the insecticide is absorbed by roots.

A soil application of the systemic insecticide imidacloprid can provide season-long control of soft scales and certain other species such as European elm scale. Imidacloprid is not effective on armored scales and certain other species such as cottony cushion scale. Imidacloprid is available to both homeowners (Bayer Advanced Garden Tree & Shrub Insect Control) and professional applicators (Merit and others). Imidacloprid can be effective when applied to soil during late winter to early spring or before rainfall or irrigation are expected to facilitate root absorption of the insecticide.