Which telltale sign on landscape trees or shrubs indicates scale insect infestation?

• A. Honeydew and sooty mold on leaves.
• B. Defoliation and silk/webbing.
• C. Sticky residue on stems.
• D. Wilting without honeydew.

Answer: (A)

Honeydew produced by sap-sucking insects like scale accumulates on leaves and other surfaces, and it invites sooty mold to grow. When you see a dark, sooty coating on foliage along with sticky honeydew, it’s a classic sign that scale insects are feeding on the plant. The mold isn’t harmful itself, but it reduces photosynthesis and weakens the plant over time, signaling an infestation that needs attention.

Defoliation with silk or webbing points to other pests such as caterpillars or spider mites, not scale. Wilting without honeydew suggests water stress or root problems rather than a scale issue. A sticky residue on stems could be honeydew, but without the accompanying sooty mold, it’s less diagnostic for scale. If you observe honeydew and sooty mold, check for scale bodies on twigs to confirm the infestation.