What is the difference between systemic and contact pesticides?

The distinction between systemic and contact pesticides primarily lies in how they interact with plants and pests. Systemic pesticides are designed to be absorbed by plants through their roots or leaves, allowing the active ingredient to circulate throughout the plant's tissues. This means that when pests feed on the plant, they ingest the pesticide, which effectively controls the pest internally. This mode of action is particularly useful for targeting pests that may not be directly on the plant's surface.

In contrast, contact pesticides operate differently. They act upon contact with pests, targeting those that are physically present on the plant's surface at the time of application. These pesticides do not require absorption into the plant and instead affect pests immediately through direct contact.

The other options present misunderstandings about these pesticide types. For instance, systemic pesticides do not repel pests or require sunlight, and there is indeed a significant difference between the two methods of action. Thus, recognizing the absorption mechanism of systemic pesticides and the contact effect of contact pesticides clarifies why the identification of these two categories is crucial in pest management strategies.