How do systemic pesticides typically reach their target pests?

Systemic pesticides are designed to be absorbed by plants and transported throughout their tissues, primarily through the plant's water and sap systems. This method allows the pesticide to effectively reach target pests that feed on or live within the plant, as it becomes part of the plant's structural or nutritional fluids. Once the systemic pesticide is taken up by the roots, it is moved through the xylem or phloem, ensuring that various parts of the plant, including leaves, stems, and roots, carry the chemical. This internal distribution is crucial, especially for pests that are not easily accessible by spraying or those that live within the plant's tissues, such as aphids or borers.

In contrast, other methods mentioned, such as spraying directly on the pests or relying solely on soil absorption, do not accurately reflect how systemic pesticides operate. Spraying is a common method for contact pesticides but not for systemic types, while soil absorption typically pertains to generating localized effects rather than the systemic reach of pesticides. Evaporation and drifting into the air do not apply to systemic pesticides since they require uptake within the plant derived from a liquid source. Hence, the correct choice reflects the fundamental mechanism of how systemic pesticides function in targeting pests effectively.