The white material is the waxy body covering of a common insect pest: White Prunicola Scale. We've received numerous questions about this scale on cherrylaurels in the past month, presumably because populations are at their highest this time of year, and therefore more noticeable. Overlapping stress on the plant from the current drought (unless you've been watering periodically) may also be adding to the plant's leaf shed or dieback symptoms, though a minor amount of inner/lower leaf yellowing and shedding is normal.

Controlling a high population of scale insects can take time, and usually involves one or more insecticides, some of which would require application by a hired professional (due to Maryland law). If you prefer to avoid using insecticides, the only recourse is to either replace plants that have too much damage or too high of a population to manage, or to brush off as many scale as you can (using something that will not abrade the bark itself) and then treat those left with a low-toxicity insecticide like horticultural oil. You can find more information in the scale page linked above, and the Introduction to Scale Insects page it connects to.

Scale insects are fragile enough that brushing them off the plant is sufficient (they cannot crawl back onto the plant, and/or their mouthparts were destroyed in the process of removal, so they will starve once removed), but dead scale that are still attached to the plant can be hard to distinguish from live scale, so even successful treatment may take a while to restore a plant's appearance and vigor.

For now, if you keep the plants, monitor the plants for watering needs to they are less likely to suffer from winter damage due to dehydration, and better able to tolerate pests like scale insects. (If you decide to replace the plants, it might be better to wait to replant until spring, as planting evergreens this late in the season risks more winter damage.)

Miri