European Elm Scale
Gossyparia (=Eriococcus) spuria (Modeer)
Dieback of twigs and branches of elm trees is a common symptom of European
Elm Scale feeding injury.
The black discoloration on the upper surfaces of the branches is due to `Sooty
Mold' colonizing honeydew produced by feeding scale. Honeydew drips on
leaves, upper surfaces of branches, on the tree trunk and people, cars and
anything else underneath.
Note the scale on the twig. The female is soft and immobile, olive-green
to reddish-brown with a white waxy fringe around the edge of the body. The
male is rarely seen, and `gnat-like'. The leaf is shiny (and sticky) from
the honeydew produced by the scale.
References Used:
Cranshaw, W., D. Leatherman, & B. Kondratieff. Insects that feed on Colorado
Trees and Shrubs. Bulletin 506A, Colorado State University Cooperative Extension.
Johnson, W.T. & H.H. Lyon. 1976. Insects That Feed on Trees and Shrubs:
An illustrated Practical Guide. Cornell University Press