Which pesticide is NOT an organophosphate?

Imidacloprid is the correct choice as it is not an organophosphate. Instead, it belongs to a class of pesticides known as neonicotinoids, which act on the nervous system of insects by targeting nicotinic acetylcholine receptors. This mechanism is distinct from organophosphates, which inhibit the enzyme acetylcholinesterase, leading to a buildup of acetylcholine and subsequent overstimulation of the nervous system.

On the other hand, chlorpyrifos, malathion, and diazinon are all classified as organophosphate pesticides. They function by interfering with the normal functioning of the nervous system in pests, making them effective in controlling a variety of insects. Understanding the chemical classification and mode of action of these pesticides is crucial in environmental science and pest management.