Scale insects: armored vs soft scale

Scale insects are among the most commonly overlooked garden pests because they do not look like insects. They attach to bark, stems, and leaves and, once settled, remain stationary for most of their life cycle. Inexperienced gardeners often mistake scale colonies for bark texture or disease lesions.

Scale insects are among the most commonly overlooked garden pests because they do not look like insects. They attach to bark, stems, and leaves and, once settled, remain stationary for most of their life cycle. Inexperienced gardeners often mistake scale colonies for bark texture or disease lesions — and the plant continues to decline while the infestation grows.

There are two major groups: armored scales (Diaspididae) and soft scales (Coccidae). They look different, cause different symptoms, and respond differently to treatment. Getting the ID right is the first step.

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What is a scale insect?

Scale insects are true bugs (Hemiptera) that feed by inserting a needle-like stylet into plant tissue and extracting phloem sap. Females are permanently sedentary after the mobile "crawler" stage — they settle, feed, and cover themselves with a protective coating. Per UC IPM, it is typically the female that causes damage; males are tiny and short-lived.