What is the IRAC sub-group for DDT?

• A. 1A, nicotinic receptor agonists
• B. 2C, cholinesterase inhibitors
• C. 4A, juvenile hormone mimics
• D. 3B, methoxychlor sodium channel modulators

Answer: (D)

IRAC classifies insecticides by how they affect the insect nervous system, which helps guide resistance management. DDT works by interfering with voltage-gated sodium channels in nerve membranes, keeping channels open and causing prolonged nerve excitation that leads to paralysis. This mechanism places DDT in the sodium channel modulators category.

Within IRAC, sodium channel modulators are grouped as a specific MoA category, and the organochlorines, including DDT, fall into a sub-group that covers these sodium channel–modulating compounds. The best match is the sub-group for sodium channel modulators that includes DDT (and related organochlorines like methoxychlor).

So the correct classification is the sodium channel modulators sub-group, which is why the option describing 3B with sodium channel modulators is the right choice. The other options describe modes of action that do not match DDT’s effect on sodium channels (for example, nicotinic receptor agonists, acetylcholinesterase inhibitors, or juvenile hormone mimics).