What is the difference between contact and systemic insecticides in turf?

What is the difference between contact and systemic insecticides in turf?

• A. Systemic insecticides kill on contact only.
• B. Contact insecticides are absorbed and translocated, providing interior protection.
• C. Contact insecticides kill on contact or via surface exposure; systemic insecticides are absorbed, translocated, and provide interior protection against feeding.
• D. All insecticides are either contact or systemic, with no other modes.

Answer: (C)

Understanding how insecticides reach the pest is the key. A contact insecticide works on pests that touch the treated surface or ingest residues on that surface; it does not rely on moving inside the plant to kill pests. A systemic insecticide, on the other hand, is absorbed by the plant and moved through its tissues so that pests feeding on those tissues ingest the chemical from within the plant, providing protection from the inside. In turf, this means systemic products can protect new growth and roots as the chemical is transported by the plant’s vascular system, while contact products act only where they’re applied on surfaces. The description that combines both ideas—contact insecticides kill on contact or via surface exposure, while systemic insecticides are absorbed, translocated, and provide interior protection against feeding—best captures the difference.

Understanding how insecticides reach the pest is the key. A contact insecticide works on pests that touch the treated surface or ingest residues on that surface; it does not rely on moving inside the plant to kill pests. A systemic insecticide, on the other hand, is absorbed by the plant and moved through its tissues so that pests feeding on those tissues ingest the chemical from within the plant, providing protection from the inside.

In turf, this means systemic products can protect new growth and roots as the chemical is transported by the plant’s vascular system, while contact products act only where they’re applied on surfaces. The description that combines both ideas—contact insecticides kill on contact or via surface exposure, while systemic insecticides are absorbed, translocated, and provide interior protection against feeding—best captures the difference.