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UPSC Prelims 1991 · Agriculture · Farming Green
Which one of the following is useful for biological control of pests?
- (a) Honeybees and locusts
- (b) Scorpions and spiders
- (c) Wasps and birds
- (d) Parrots and kites
Show the answer and explanation
Answer: (b) Scorpions and spiders
Spiders and scorpions are predators that eat insect pests.
Why the others are wrong
(a) Locusts are pests themselves.
(c) Wasps and birds also control pests — a strong alternative.
(d) Parrots damage crops.
The trap
(c) is also biologically sound; the key picks (b).
🔒 Biocontrol agents: Trichogramma wasps, ladybirds, spiders, Bt, NPV.