Lemongrass: The Grass Behind Natural Mosquito Repellents

Lemongrass

• The UPSC 2021 answer is lemongrass.
• Two plants share the name.
• Cymbopogon citratus is widely used in food and tea.
• Cymbopogon flexuosus is a major Indian oil crop.
• Citral gives the oil its lemon smell.
• Some oils also have small amounts of citronellal.
• Citronella grass is a close relative, not a synonym. Citronella oil comes from C. nardus or C. winterianus.
• A leaf alone does not give reliable bite protection.
• Sources: ICAR, CSIR and plant-chemistry review.

From leaf to oil

1. Grow and cut the leaves.
2. Use steam to lift the oil.
3. Cool it and separate the oil from water.
4. Test and blend a product.

• CSIR has bred lemongrass types for oil.
• The oil goes into scents, soaps, flavours and some repellent formulas.
• An ICAR farmer-producer example describes growers who distil their crop and sell citral-rich oil.
• Income depends on yield, quality and market price.
• Sources: CSIR technologies and ICAR farmer-producer case.

What a repellent can really do

• A repellent makes a person less attractive to a biting insect. An insecticide kills it.
• Studies show some protection from lemongrass or citronella oils.
• A tested blend does not prove a homemade oil works as well.
• These oils evaporate fast. A US EPA review of citronella products found protection may fade within one or two hours.
• Do not rely on a potted plant or candle alone in a dengue or malaria area.
• “Natural” does not mean harmless to skin.
• Sources: US EPA, what repellents do, US EPA citronella review, US EPA, regulation and WHO testing guidance.

• Congress grass can crowd crops and pasture.
• Studies cited by Indian wildlife researchers report crop losses up to 40% and forage losses up to 90% in some settings.
• These are upper estimates, not national averages.
• Pune is often named as its first modern Indian record, in 1955. Older herbarium evidence may point earlier.
• Sources: Wildlife Institute of India review and EPPO datasheet.