How does a systemic insecticide act on the pest?

A systemic insecticide functions by being absorbed into the tissues of a plant after it has been applied. Once the insecticide is inside the plant, it moves through the plant's vascular system, which allows it to be present in the leaves, stems, and other parts. When pests feed on the treated plant, they ingest the insecticide. This method of action is particularly effective against sucking insects, like aphids and spider mites, which feed on plant sap.

The systemic nature ensures that the insecticide can provide control even if the pests are not directly in contact with the application site. This characteristic differentiates systemic insecticides from contact insecticides, which require direct application onto the pest to be effective. As a result, the method of action of systemic insecticides makes them a potent option for targeting pests that may be concealed within the plant tissue or for those that infest plants where surface applications might not reach them effectively.