European Elm Scale: Appearance, Territory, Damage and Life

Latin name: Gossyparia spuria

Appearances: Females reach a maximum size of 10 mm, are oval, reddish-brown, and have a white, waxy fringe. When scales are broken, a blood-like, red liquid is produced. Males are smaller than females and have white, puffed rice-like cocoons. immatures: wingless nymphs that are flattened and oval; crawlers (mobile stage) that are 3/64 inches long and yellow orange; translucent yellowish overwintering immatures with a light gray-white waxy coating.

Host plants: They prefer American and rock elm, which they devour.

Territory: Eriococcus spuria’s, formerly known as Gossyparia spuria, is a scale insect that was introduced to North America.

Damage insect caused: Because of the production of sticky honeydew (excrement), European elm scale can become an annoyance, especially in June and early July. Sooty mold that is forming on the honeydew frequently causes blackening of neighboring surfaces and branches. Scale feeding can cause premature leaf drop and yellowing (flagging) of the leaves. Strong infestation may lead to branch dieback in healthy trees and the death of weakened trees. A narrow canopy is frequently a sign of a severe infestation. Long-term infections weaken branches, frequently resulting in early leaf fading. Sap-sucking can result in branch dieback, premature leaf loss, and stunted, chlorotic foliage.

Life cycle and habits: The second instar nymphs of the European elm scale spend the winter crammed into fissures in twigs and smaller branches. Due to the delicate waxy covering on the body, they are generally oval and pale grey in colour. They resume developing in the spring, and the females substantially enlarge, darken, and acquire a distinctive waxy fringe. Male scales may start emerging from tiny white cocoons in the late April and early May in order to mate with the females. Although this species can reproduce asexually, males are not usually produced.

Within the female’s body, eggs hatch, and crawlers appear over a period of weeks, peaking between mid-June and mid-July. The dark yellow nymphs travel to leaves and settle there, almost often hiding close to the major leaf veins. They return to the twigs where they spend the winter in the late summer.