How do systemic insecticides typically work?

Systemic insecticides are designed to be absorbed into the plant tissue, which allows them to protect the plant from pests that feed on it. When these insecticides are applied to the soil or foliage, they enter the plant’s vascular system and circulate throughout the plant's tissues. This method of action is particularly effective because it enables the insecticide to remain within the plant for an extended period, providing ongoing protection as pests attempt to feed.

The absorption mechanism ensures that the active ingredient is available throughout the plant, making it lethal to various pest life stages that consume plant material, such as larvae and adult insects. This targeted mode of action is more efficient than methods that rely on direct spraying or contact, where protection may be limited to the areas that were treated.

Other options present methods that do not align with the operational principles of systemic insecticides. For instance, simply evaporating quickly would not allow for effective pest control, while repelling pests does not rely on the insecticide being internalized in the plant. Additionally, the notion of killing only adult insects is too restrictive, as systemic insecticides can affect all developmental stages of the pests that feed on the treated plant.