Eucalypt Insects



Gumtree scale

Eriococcus coriaceus



Female gumtree scale (Eriococcus coriaceus)
? Agriculture Western Australia

The female scale grows 3 - 4 mm long and is fixed to small stems, branches and near the midrib of leaves. The felted globular sac which encloses each adult varies from white or yellow to dark brown and when squashed contains a reddish fluid. The male scales are smaller, being 1 - 2 mm long, white and more elongated than the females and are often clustered above the females on the stems or leaves.

Life cycle
The female scale is not mobile and lays its eggs within its protective sac after being fertilized by the small winged males, which emerge from their white sacs to find them. When the eggs hatch, the young mobile nymphs emerge from the female sac to migrate to other stems and leaves where they produce fresh sacs and continue their development. There may be five generations during a year depending on the season. Summer generations are completed in about 50 days compared with about 85 days in winter. Greatest debilitation of trees can therefore be expected to occur in late summer at the time of highest drought stress.

Infestation on Eucalypt stems and foliage
? Agriculture Western Australia

Gumtree scales infest young stems and leaves, sucking the sap and producing a sugary secretion which may cover the leaves and cause them to glisten. A sooty mould fungus often infects this secretion and causes the leaves to turn black. Ants commonly attend the scales to feed on their sugary exudate, which they promote by stroking the scales. Continued attack results in debilitation of the tree and small trees may die. A number of eucalypts are attacked by this scale, but in Western Australia wandoo is probably the most commonly infested, particularly in the wheatbelt.