Cottony cushion scale

Definition

A conspicuous, polyphagous scale insect (Icerya purchasi, family Monophlebidae) recognizable by the female's large, white, fluted ovisac that resembles cotton batting. Native to Australia, it is a major pest of citrus and ornamental woody plants worldwide, historically controlled by the vedalia beetle (Rodolia cardinalis) in the first successful case of classical biological control.

Etymology

From the cottony appearance of the female's egg sac (ovisac) and the cushion-like body of the adult female scale.

Example

In California citrus groves, cottony cushion scale populations were devastated after the 1888 introduction of the vedalia beetle from Australia, establishing the economic value of imported natural enemies against exotic pests.

Synonyms

• Icerya purchasi
• fluted scale

Related Terms

• scale insect
• Monophlebidae
• vedalia beetle
• Biological control
• ovisac
• citrus pest
• polyphagy
• Parthenogenesis

Usage Notes

The common name refers specifically to Icerya purchasi, though related Icerya species may appear similar. The species is notable for being ovoviviparous and hermaphroditic, with males rare. In field identification, the white ovisac distinguishes it from armored scales (Diaspididae), which lack such structures. The term is sometimes hyphenated (cottony-cushion scale) in older literature.