What are systemic insecticides and how do they work?

Systemic insecticides are a type of pesticide that is absorbed by plants, allowing them to protect themselves against pests that feed on them. Once applied, these insecticides enter the plant's vascular system and can be translocated throughout various tissues, including leaves, stems, and roots. When pests such as aphids or leafhoppers feed on the plant, they ingest the insecticide along with the plant tissues, which ultimately affects their nervous system or other critical functions, leading to pest mortality.

This mechanism is particularly effective for controlling pests that are not easily targeted with contact insecticides, as it provides a more thorough level of protection for the plant. The systemic action ensures that even pests hiding within the plant or those that are difficult to reach can be affected.

The other options focus on different forms and methods of action concerning pesticides. The application on soil only pertains to a specific type of treatment and does not capture the essence of systemic action. Aerosol treatments are effective but primarily target pests in the air and do not involve plant absorption. Additionally, targeting only surface-feeding insects limits the scope of systemic insecticides, as their purpose is to protect the entire plant, regardless of which insect may be feeding on it.