What is a systemic pesticide?

A systemic pesticide is defined as one that penetrates the plant, meaning it is absorbed and circulated throughout its tissues. This characteristic allows the pesticide to be effective against pests that feed on or within the plant, as it targets them through the plant’s vascular system. When a systemic pesticide is applied to the leaves, roots, or soil, it is taken up by the plant and distributed throughout its entire system. This makes it particularly effective for controlling pests that might be hiding within or feeding on internal plant structures, which surface treatments might not adequately address.

In contrast to the other options, a pesticide that remains on the surface would only affect pests that come into direct contact with the treated area, limiting its efficacy against those pests that don't engage directly with the plant's surface. A pesticide effective only in soil would suggest a more localized action, rather than a broad, plant-wide effect. Pesticides that act quickly upon contact usually do not have the systemic properties required to be absorbed by the plant, focusing instead on immediate knockdown of pests upon contact rather than long-term efficacy. Thus, the ability of systemic pesticides to involve the plant’s internal systems is what distinguishes them and drives their effectiveness in pest management.