Adelgid aphids - White Fluffy Aphid Growths on Conifer. 

Adelgids are difficult to see on conifers until mid-summer when the normally black aphids, cover themselves in a white woolly fleece for protection.  Young conifers can suffer a worrying degree of damage, but the Adelgids can also affect mature specimens if not treated. As they bore into the bases of the leaflets, this can cause leaf (needle) drop resulting in a weakening of the conifer if not controlled.

Conifers are relatively trouble free plants suffering little in the way of problems. Regular inspection should be carried out on prized specimens to catch such pests before they do too much damage.

The aphids bore through the bark of young conifer twigs, and often leave scar tissue after the infestation.

Systemic insecticide such as Provado, or drench them with contact insecticide containing Bifenthrin. In late autumn, good specimen conifers can be sprayed with horticultural oil. This will kill most overwintering pests before they cause damage the following spring.