How can I distinguish scale insects from similar pests?
Written by
Liu Xiaohui
Reviewed by
Prof. Martin Thorne, Ph.D.Scale insects can often be misidentified and are usually indistinguishable from other pests or plant parts. I have watched gardeners spray aphids, believing they were scale insects, wasting valuable time and chemicals in the process. The scales have smooth, shell-like coverings that distinguish them from mealybugs, which have fluffy, waxy coverings. Scales remain fixed in one area when settled, compared to aphids that crawl around when they are more active.
Mealybugs
- White cottony appearance unlike hard scale shells
- Produce honeydew similar to soft scales
- Mobile throughout life unlike stationary adult scales
Plant Buds
- No sticky honeydew secretion when pressed
- Uniform shape unlike irregular scale formations
- Part of natural growth not parasitic
Aphids
- Soft bodies without protective covers
- Visible antennae and legs unlike concealed scales
- Leave shiny honeydew without waxy residues
The magnolia scale resembles a tightly closed bud of a flowering plant until you notice some dried honeydew. Take a tissue and wipe underneath the bump to check for the sticky residue. I teach my clients to do the tape test: touch clear tape to the suspected scales. If there are insects stuck to the tape, then you confirmed it's a scale infestation rather than natural plant growth.
When you find the somewhat mobile nymphs, it is certainly a matter of scale identification. These tiny, somewhat mobile nymphs emerge only during certain times of the year. They appear slowly rather than thrips seemingly jumping off scales. Yellow sticky traps placed around the plants will capture chewing insects. This indicates an active infestation that requires treatment.
Read the full article: Mastering Scale Insect Identification: A Complete Guide
