Associate Certified Entomologist (ACE) Practice Exam

Which of the following is an example of an organophosphate?

1. Carbaryl

2. Chlorpyrifos

3. Boric acid

4. Propanil

The correct answer is: Chlorpyrifos

Chlorpyrifos is a well-known organophosphate insecticide used for controlling various pests in agricultural and residential settings. Organophosphates function by inhibiting cholinesterase, an enzyme essential for the proper function of an insect's nervous system. This inhibition leads to the accumulation of acetylcholine, resulting in continuous stimulation of muscles, glands, and central nervous system functions, ultimately causing the pest's death. Carbaryl is a carbamate insecticide, not an organophosphate, and while both groups share similar modes of action, they are chemically distinct. Boric acid is a mineral compound often used as an insecticide, but it does not fall under the organophosphate category. Propanil is a herbicide that is also not an organophosphate. Thus, chlorpyrifos stands out as the representative example in this context.