Fern Scale

Definition

A common name for Pinnaspis aspidistrae (Signoret, 1869), a diaspidid scale insect (family Diaspididae) that infests ferns, Aspidistra, and other monocotyledonous ornamentals. Females produce elongated, oystershell-shaped, brownish tests (protective coverings) aligned along leaf midribs and veins; males form smaller, narrower tests. The species is parthenogenetic in many populations and is a significant greenhouse and nursery pest worldwide.

Etymology

Common name derives from its primary host association with ferns (Pteridophyta) and its armored scale morphology.

Example

Heavy infestations of fern scale on Boston fern (Nephrolepis exaltata) cause yellowing fronds, premature leaf drop, and conspicuous brown oystershell tests along pinnae midribs; crawler dispersal peaks in warm, humid greenhouse conditions.

Synonyms

• Pinnaspis aspidistrae
• oystershell scale (misapplied, reserved for Lepidosaphes ulmi)

Related Terms

• Diaspididae
• armored scale
• test
• Crawler
• Parthenogenesis
• Aspidistra scale
• greenhouse pest

Usage Notes

The common name 'fern scale' is sometimes loosely applied to other fern-feeding diaspidids, but properly refers to Pinnaspis aspidistrae. Not to be confused with Lepidosaphes ulmi (oystershell scale) on woody plants. The elongated, parallel-sided female test distinguishes it from circular armored scales such as Chrysomphalus species.