Neem and Tulsi plants as mosquito repellents

Question

Why do we use neem and tulsi plant to keep mosquitoes away from our home?

Answer

Many plants produce volatile or toxic compounds as a way of deterring herbivores and plant-eating insects. Many of these compounds are also repellent to insects of the order Diptera, which includes mosquitoes and many different kinds of flies, possibly suggesting a plant-eating ancestor, or a conserved recognition of toxic chemicals. As the chemicals are more readily released when the plant is damaged, hanging bruised insect-repelling plants in the house is a traditional method for deterring mosquito bites. Alternatively, the plant can be burned, dispersing the repellent chemicals.

The neem tree, also known as Indian Lilac, is a fast-growing tree native to the Indian subcontinent, known for its insect-repelling properties, among a variety of other uses. The active ingredient in the neem plant is thought to be azadirachtin, and a large number of similar chemicals. The effectiveness of neem as a mosquito repellent varies depending on the method of use – field studies have returned protection levels of 94.2% (by dispersing the oil with a kerosene lamp), 76% (from burning the leaves) and 56.75% (by applying 2% neem oil to a person). Neem is used preferentially over some other preparations, as it is non-toxic and biodegradable, so can be applied directly to the skin, or spread over crops.

Tulsi or tulasi is also known as holy basil, hence its Latin name Ocimum sanctum. This plant is also commonly used as a mosquito repellent, though it has also been investigated as an antibacterial and an anti-inflammatory agent, among other potential medicinal uses. Few studies have been conducted measuring the efficacy of tulsi as a mosquito repellent, though in one study the burning of its leaves was sufficient to keep away 80% of mosquitoes. It is also known to be an effective larvicidal of several mosquito species.

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