This white fluffy substance on your boxwood is a waxy secretion produced by an insect called Boxwood Psyllid, a fairly common pest of boxwoods.

Their feeding causes the leaves to cup and curl, but it is primarily cosmetic damage and not detrimental to the overall health and life of the shrub. Fortunately, these insects have just one generation per year.

You can try removing some of the white wax with a strong spray of water from a garden hose. You could also prune and thin the plant to take out the most affected branches or use a horticulture oil (available at garden centers) to control the insects. Read and follow product label instructions.

Your boxwood looks like it could benefit from pruning. The best technique is thinning. It lets in sunlight and provides good air circulation. See the attached link for our pruning video https://extension.umd.edu/resource/volutella-blight-disease-boxwood

Here is more information on our website:

https://extension.umd.edu/resource/boxwood-psyllid-insects-shrubs

https://extension.umd.edu/resource/boxwood-diagnose-manage-and-prevent-common-problems

Marian