Which symptom is characteristic of sap-feeder attack on ornamental plants?

The characteristic symptom of sap-feeder attack on ornamental plants is stippling on leaves. Sap-feeders, such as aphids and spider mites, extract sap from plant tissues, which can cause localized damage. This feeding results in small, pale spots or stipples on the leaves, as the loss of chlorophyll occurs in those areas. The effect is often seen as a pattern of discoloration, giving the leaves a speckled appearance that can reduce the plant's overall vitality and aesthetic quality.

In contrast, bacterial wilt is typically linked to pathogens that affect the vascular system of the plant, leading to wilting, and does not relate to sap-feeding behavior. Blackening of roots often suggests issues related to root rot or poor soil conditions rather than sap feeding. Leaf curling can occur for various reasons, including environmental stress or viral infections, but it is not a specific symptom tied to sap-feeding insects. Stippling is the most direct indicator of feeding damage from sap-feeders on ornamental plants.