What is the key difference between systemic and contact pesticides?

The key distinction between systemic and contact pesticides lies in how they interact with plants and pests. Systemic pesticides are designed to be absorbed by plants, which allows them to move throughout the plant's tissues, including leaves, stems, and roots. This means that when pests feed on any part of a plant treated with systemic pesticides, they are exposed to the active ingredient, even if they do not come into direct contact with the pesticide during application.

In contrast, contact pesticides work on the principle of immediate action on the surface where they are applied. They do not penetrate the plant tissues, meaning their effectiveness relies on direct contact with the pest. If pests are not present on the treated surface when it is applied, they will generally not be affected.

The implication of this difference is significant for pest management strategies. While systemic pesticides can provide longer-lasting protection by affecting pests that feed on the plant over time, contact pesticides may require more frequent reapplications to maintain their effectiveness, as their action is limited to the surface area where they are sprayed.