pests and diseases
Scale insect
Last reviewed 2026-10-04
A scale insect is a sap-feeding insect that often appears as a small bump, shell, or waxy covering attached to a stem, leaf, or fruit. Some scales move during an early stage and then settle, while others remain more mobile. Feeding can weaken plants and produce honeydew.
What it means
Scale insects vary widely in appearance and life cycle. The protective covering can make them difficult to reach with a treatment, and the useful control window may be the mobile crawler stage. Ants may visit honeydew-producing scales and protect them from predators.
How it affects the garden
Inspect stems and leaf veins on new plants and houseplants. Isolate infested containers when practical, prune lightly infested parts, and use a targeted method suited to the plant and scale type. Avoid treating a plant without identifying the pest because armored and soft scales can respond differently.
IPM begins with confirming the pest and measuring damage. The can I grow this tool helps site planning but does not identify scale.
Example
A citrus plant develops small brown bumps along stems and sticky leaves. The gardener checks whether the bumps scrape off, looks for crawlers, and examines the plant before selecting a control.
Common confusion
Scale is not a fungal spot or a natural stem bud. Look for a consistent insect pattern and associated feeding signs.
Sources
University of Minnesota Extension explains scale insect types, life cycles, and management.
