Systemic pesticides can be especially useful because they can...

Systemic pesticides are designed to be absorbed by plants and distributed throughout their tissues. This characteristic makes them uniquely effective for targeting pests that may be feeding on various parts of the plant, such as leaves, stems, or roots. Once the pesticide is absorbed, it can move through the vascular system of the plant, reaching insects that feed on those tissues.

This internal distribution means that even pests that are not directly contacted by the application can still be affected when they ingest plant parts that contain the systemic pesticide. This is particularly valuable for controlling pests that are difficult to reach or that hide within plant structures.

The other options do not accurately describe the function of systemic pesticides. For instance, while some pesticides do kill pests on contact, systemic pesticides operate differently by spreading throughout the plant. Similarly, systemic pesticides do not solely target the root systems, nor are they designed to act as repellents; their main purpose is to eliminate pests by internal absorption and subsequent ingestion by feeding insects.