How do contact pesticides differ from systemic pesticides?

Contact pesticides are designed to take effect when they come into direct contact with pests. This means that their mode of action relies on the pesticide physically touching the target pest to be effective. These pesticides usually work by penetrating the pest’s exoskeleton or entering through the skin, leading to its death shortly after application.

In contrast, systemic pesticides operate differently. They are absorbed by plants and transported throughout their tissues, allowing the pesticide to act on pests that feed on the plant, even if the pests do not come into direct contact with the pesticide itself. This characteristic makes systemic pesticides effective against pests that may not be present on the exterior of the plant, as they can interfere with various physiological processes in the pest when ingested.

By understanding this fundamental difference, one can appreciate why contact pesticides require thorough coverage of the pest population for effectiveness, while systemic pesticides provide a broader form of protection by affecting pests that consume plant material.