Which of the following is not an organophosphate insecticide?

The correct answer is that pyrethrum is not an organophosphate insecticide. Pyrethrum is derived from the flowers of the chrysanthemum plant and is considered a natural insecticide. It works by affecting the nervous system of insects, leading to paralysis and death. Unlike organophosphates, which are synthetic chemicals that inhibit specific enzymes necessary for normal nerve function, pyrethrum functions through a different mechanism that involves disruption of neuronal impulses due to its rapid effect on sodium channels.

Organophosphate insecticides, such as malathion, chlorpyrifos, and diazinon, all operate by irreversibly inhibiting acetylcholinesterase, an enzyme critical for nervous system function. This leads to an accumulation of acetylcholine and subsequent overstimulation of the nervous system in target organisms. Recognizing the differences between these classes of pesticides is key to understanding their application, safety, and environmental impacts, which makes it vital for pest control professionals to differentiate them effectively.