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UPSC Prelims 2021 · Environment · Species Watch
Which one of the following is used in preparing a natural mosquito repellent?
- (a) Congress grass
- (b) Elephant grass
- (c) Lemongrass
- (d) Nut grass
Show the answer and explanation
Answer: (c) Lemongrass
Lemongrass and its relative citronella grass give the oil used in natural repellents.
The idea
A mosquito finds us by smell. The strong lemon-scented oil of lemongrass and its relative citronella grass hides that smell and drives mosquitoes away.
Lemongrass / citronella: scented oil → repellent, perfume, soap → Congress grass (parthenium): an invasive weed that causes allergy → Elephant grass (Napier): cattle fodder → Nut grass: a stubborn farm weed
Why the others are wrong
(a) Congress grass (Parthenium) is an invasive weed that causes allergies.
(b) Elephant grass is fodder.
(d) Nut grass is a stubborn weed.
Also know
Other scented grasses grown for oil: palmarosa and vetiver (khus). Parthenium came to India by accident with imported wheat in the 1950s.
🔒 Lemongrass / citronella oil = natural mosquito repellent. Parthenium = invasive weed.