The plant sounds like Pyracantha and like other members of the Pomme section of the rose family (apples, pears, cotoneaster etc) they can suffer sometimes severe infestations of woolly aphid on their stems. There is a product called Provado that you could try but only use it well before any flowers are on the plant as it is very toxic to bees which carry the poison back to their nests, wiping the whole colony out in the process (certainly Bumble Bees).