It's called boxwood blight. It hits two most commonly planted kinds of boxwood, which is American boxwood and dwarf English boxwood. And the signs of this are that you'll start to see brown spots ...

On the Royal Horticultural Society’s web page ‘Box: Problems’ it is clear that there are many other sap-sucking insects queuing up to destroy anyone’s dream of an English ... by dwarf yew. Conifers ...