Which one of the following is used in preparing a natural mosquito repellent?
Answer & explanation
Answer: (c) Lemongrass
Lemongrass (Cymbopogon species) yields an aromatic essential oil rich in citral, and this oil is used in insect-repellent preparations and has been shown to repel mosquitoes. Congress grass (Parthenium) is a weed, and elephant grass is a fodder grass.
- ✓ (c) Lemongrass oil, distilled from the leaves, has a strong lemon-like smell from its citral and goes into insect-repellent preparations (National Horticulture Board); laboratory studies show it repels mosquitoes.
- ✗ (a) Congress grass is Parthenium hysterophorus (carrot grass), an invasive weed that causes pollen allergy; it is not used to repel insects.
- ✗ (b) Elephant grass (Napier grass, Pennisetum purpureum) is a tall tropical grass that gives good fodder for grazing animals when young; it is not a repellent.
Remember · Lemongrass (Cymbopogon) oil, rich in citral, is a plant-based mosquito repellent. Congress grass (Parthenium) is an invasive weed; elephant (Napier) grass is fodder.
📘 Read it in NCERT: Class 12 Biology, Ch 1 (practise this chapter) · Class 12 Biology, Ch 13 (practise this chapter)
Sources
- National Horticulture Board (Government of India), Lemon Grass ↗ “The characteristic smell of oil makes its use in scenting of soaps, detergents, insect repellent preparations.”
- CSIR-CIMAP Aroma database: Cymbopogon (lemongrass genus) ↗ · reference work “which is used in soaps, as an insect repellent (especially mosquitoes) in insect sprays and candles, and in aromatherapy”
- Baldacchino et al., 'The repellency of lemongrass oil against stable flies', Parasite (2013), via PubMed Central (US National Library of Medicine) ↗ “Lemongrass oil ( Cymbopogon citratus ) is an effective repellent against mosquitoes (Diptera: Culicidae) and house flies (Diptera: Muscidae). … Lemongrass essential oil has previously shown a repellent effect, alone or in combination, against different species of disease-transmitting mosquitoes”
- NCERT Class 12 · Biology, Chapter 1 “Parthenium or carrot grass that came into India as a contaminant with imported wheat, has become ubiquitous in occurrence and causes pollen allergy.”
- Encyclopaedia Britannica, Napier grass (elephant grass) ↗ · reference work “providing good fodder for grazing animals when young but quickly becoming rank, coarse, and a refuge for insects.”
- NCERT Class 12 · Biology, Chapter 13 “invasive weed species like carrot grass (Parthenium), Lantana and water hyacinth (Eicchornia)”
Question and answer: UPSC's official GS Paper I (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). ·