Elm Scurfy Scale: Appearance, Territory, Damage and Life Cycle

Latin Name: Chionaspis Americana

Appearance: The female of the widely dispersed scale Chionaspis americana, which feeds on elm and hackberry, is coated by a dull white scale that is frequently darkened anteriorly by secretion. Adult female coverings are 3mm long, flat, dirty whitish to grey, and shaped like a pear. Male coverings are smaller and slenderer.

Hosts Plants: Aspen, Crabapple, Apple, Hawthorn, Dogwood, Mountainash willow and Elm

Territory: It is native to North America.

Damage Insect Cause: Most apple orchards in Virginia are at risk from scurfy scale, a major pest in many orchards. The scale insect damages the tree and finally kills the lower branches and tree itself. Additionally, the fruit frequently contracts an infestation and is then removed off the market for quality fruits. Heavy infestations can cause branch withering and drying. Scale coverings on ornamental plants can be ugly, leaving a white coating on the twigs and branches. Small chlorotic patches are caused by male second instars eating on leaves.

Life History and Habits: Both sexual and parthenogenetic reproduction have been documented. This is an univoltine species with eggs that overwinter beneath the scale of the parent female. In the summer, each female lays between 8 and 60 eggs, depending on host quality and environmental conditions. Crawlers are the major dispersers, moving to new parts of the plant or being spread by wind or animal contact. Abiotic factors are a major cause of death at this stage. Sessile adults and eggs are dispersed through human transport of contaminated plant material.

This species develops two generations every year and spends the winter as an egg. In late May and early July, first instars molt to second instars. Adults are visible in June and July, and females lay eggs in July. Second generation crawlers hatch in July and mature in late August and early September. Overwintering egg laying occurs from October to November. Males prefer the undersides of leaves, while females prefer the bark. Adult males are primarily apterous during the fall generation and apterous and brachypterous during the spring generation.