Beech bark scale

Symptoms
Infested trees, with or without cankers, may appear to be covered with snow. Varying sizes of white fluffy "wool" covering tiny yellowish insects on the stem are indicative of active insect attack during, or in advance of, canker formation.

The pest renders the tree to infection by fungi which causes a serious condition called beech bark disease. This in turn causes extensive cankering and deformation of the stem, rendering the trees unsuitable for any use other than as firewood.

Spot them
Mature scale insects are only about 1mm long. More distinctive are the colonies containing females, eggs and nymphs which form white, waxy, powdery coating. The scale insect overwinters (in an immature stage) on the bark covered by the white, wool-like wax.