Which causes sterility in roaches in the nymphal stage?

• A. IGRs
• B. Abamectin
• C. Fipronil
• D. Hydramethylon

Answer: (A)

The key idea is how developmental hormones control whether a nymph can mature into a fertile adult. Insect Growth Regulators mimic or disrupt juvenile hormone signaling, which tells immature insects when to molt and when to stop growing. When roaches encounter an IGR, their nymphs can’t properly complete the final molts to become adults, or their adult reproductive systems don’t develop or function correctly. This directly affects reproduction, leading to sterility or nonfunctional adults, especially when effects are seen across the immature stages.

The other pesticides listed work differently. Abamectin, fipronil, and similar compounds are neurotoxins that disrupt nerve function, causing rapid death or disablement rather than specifically altering development or reproductive capability in nymphs. So they don’t target the reproductive development pathway the way an IGR does, which is why the growth regulator is the best fit for causing sterility in nymphs.