Original Research

Development of eco-friendly herbal mosquito repellent

Susheela Palanisami*, Ezhili Natarajan, Radha Rajamma

Department of Zoology, PSGR Krishnammal College for Women, Coimbatore, Tamilnadu, India

J Innov Biol (2014) Volume 1, Issue 3: Pages: 132-136

Abstract: Mosquitoes are the most important and abundant pest in urban, sub-urban and rural environment. Although, chemical control provides quick mortality, resistance of mosquito against the use of insecticides have been widely reported. Moreover, chemical mosquito repellents contain toxic synthetic pyrethroids as active ingredients whose exposure to food and water is hazardous to health. In the present study, an attempt has been made to develop an eco friendly mosquito repellent sprayed with lemon grass oil. It is an established fact and practice is that the natural mosquito repellent is more effective and keeps environment pleasant and eco friendly. Raw materials have been selected based on experience and practice by ancestors. The formulation is safe, eco-friendly, cheap, easy to use and has maximum repellence against mosquitoes. In addition this, the mosquito repellent is less harmful to our health than the ones available in the market.

Received: 18 May 2014
Accepted: 05 June 2014
Published Online: 03 July 2014

Corresponding Author:
Palanisami S.,
Department of Zoology, PSGR Krishnammal college for women, Coimbatore, Tamilnadu, India
email: susheelasomu@gmail.com

Keywords: Repellent, pesticide, mosquito, repellent, essential oil

IntroductionMaterial & MethodsResults & DiscussionFigures & TablesReferences
Mosquito borne diseases are major human health problem in all tropical and subtropical countries. The diseases transmitted include malaria, filariasis, yellow fever, Japanese encephalitis and dengue fever Culex quinquefasciatus, the potential vector of lymphatic filariasis, is the most widely distributed tropical disease with around 120 million people infected worldwide and 44 million people having common chronic manifestation (Bernhard et al. 2003). Controls of such serious diseases are becoming increasingly difficult because of the high rate of reproduction and development of resistance to insecticides in mosquitoes (Sukumar et al. 1991).
Synthetic pesticides have been extensively used for mosquito control by either killing, preventing adult mosquitoes to bite human beings or by killing mosquito larvae at the breeding sites of the vectors (Brown, 1986.) However its deleterious impact on non-target population and the development of resistance prompted for the search of alternative, simple and sustainable methods of mosquito control. The need for development of effective insecticides should be taken into consideration due to the toxicity problems, together with the increased incidence of insect resistance (Miro specos et al. 2010).In most parts of the world, Synthetic chemical larvicides continue to be applied for controlling mosquitoes but many of these chemicals are toxic to human, animal and plant life and resistance can be problematic in regulating the control. Therefore, researchers are currently exploiting natural substances to be used as insecticides for controlling larval mosquitoes.
According to a recent WHO pesticide evaluation, the main insecticides used against mosquitoes in the Americas are pyrethroids and organophosphates (Kassir et al.1989).Some of the common chemical-based insect repellents used for mosquitoes are DEET (N,N-diethyl-m-toluamide)which is a registered pesticide, but possible side effects and warnings include: skin and eye irritation, insomnia etc. Permethrin, resmethrin and sumithrin are also other synthetic pyrethroids commonly used in mosquito control programs to kill adult mosquitoes. Many plant extracts have been identified as having insect-repellent effects and there has been increasing research in the last decade proving plant-based insect repellents are just as, if not more effective than DEET like Eucalyptus oil, Citronella Oil, Neem Oil etc. Most of the South Asian countries are based on agriculture and subsequent farming hence since time immemorial the benefits of cow dung have been explored and tested from being used as a fertilizer, medicine, fuel source and now most importantly to obtain biogas(Elangovan et al.2009) .In India the cow is an object of worship, for centuries and cow dung is used for many purposes. It has various medicinal values- some use cow urine to treat acne, it is used as seed protector, mosquitoes repellent and an ingredient in making bricks and it can also treat skin sores.
In ancient medical system the world over practice of treating diseases with the use of cow dung was prevalent. It is a proven fact that medicinal properties are present in the cow dung cakes and the resultant smoke that emanates after burning them. Cow dung contains plenty of Menthol, Ammonia, Phenol, Indol, Formalin and specifically its bacteriophages eradicate the pathogens and are a recognized disinfectant (Mohan et al. 2007). Cow dung usage has a prominent importance in India since past few thousands of years in the areas of medicine, agriculture/farming, atmospheric protection, etc. Cow dung mainly constitutes of carbon, hydrogen, oxygen and small amounts of nitrogen and during combustion, carbon dioxide, water vapour and ash are produced.
Plants products are emerging as a potential source of mosquito control and among them essential oils have special interest due to their insecticidal properties (Benner, 1993). Essential oils are volatile naturally occurring, complex compounds characterized by a strong odour and are formed by aromatic plants as secondary metabolites (Madhumathy et al.2007). They are liquid, volatile, rarely coloured, lipid soluble and soluble in organic solvents with a density generally lower than that of water. There are 17,500 aromatic plant species among higher plants and approximately 3,000 essential oils are known out of which 300 are commercially important for pharmaceuticals, cosmetics and perfume industries apart from pesticide potential. In nature essential oils play an important role in the protection of the plants as antibacterial, antiviral, antifungal, insecticides and also against herbivores by reducing their appetite for such plants (Rahuman et al.2007). They also may attract some insects to favour the dispersion of pollens and seeds or to repel the undesirable. Owing to the attraction for natural products like essential oils, despite their wide use and being familiar to us as fragrances, it is important to develop a better understanding of their mode of biological action for new applications in human health, agriculture and the environment(Karmegan et al.1997). Some of them constitute effective alternatives or complements to synthetic compounds of the chemical industry without showing the same secondary effects.
Hence the present study aims to develop an eco-friendly mosquito repellent, a substitute for chemical repellent by using cow dung and lemon grass essential oil and to produce the natural repellent which is more cost effective, cheap and keeps the environment pleasant and health friendly.
The raw materials used for the production of the eco friendly mosquito repellent are Cow dung, Neem leaves, Nerium flowers, Saw dust, Loban, Tulsi, Maida and Lemon grass oil (Figure 1). Cow Dung has large ash content, has large volatile content, low carbon content and burning ratio is low, meanwhile the saw dust will enhance the combustion process. Loban (sambarani) is a resin from a tree (Styrax benzoin) and is an excellent repellent of insects and mosquitoes. The fumigation of Loban is a good insect repellent. It has qualities of an insecticide, is antiseptic and fights epidemics. Its smoke creates a soothing atmosphere of calm serenity. Tulsi and Lemon grass are the most generally used medicinal plants and it has excellent antiviral and insecticidal property. Neem leaves has antiviral and natural mosquito repellent properties. Apart from these ingredients, Maida acts as an excellent binder.
Neem leaves, Tulsi and the Nerium flowers were collected from in around PSGR Krishnammal College campus, Coimbatore, Tamilnadu and were allowed to dry in the shade. The dried neem leaves and Nerium flowers are mixed with the loban and saw dust and it is ground well to get a powered form which is then mixed with the cow dung along with maida. The mixture is pressed into the desired shapes with the help of a mould which was then dried with the help of a drier (Figure 2). Lemon grass oil was sprayed on top of the coil by using a hand spray pump. The coil was dried in the oven at 700c for 6 hours, and further kept in the room for half an hour of drying. Finally these coils were packed in a suitable air tight and kept for 2 – 3 days for storage for the essential oil to spread uniformly on the coil.
Smoke Toxicity Test

The experiments were conducted in glass chamber measuring 140 x 120 x 60 cm and a window measuring 60 x 30 cm was situated at mid bottom of one side of the chamber. Three or four day’s old blood starved adult female mosquitoes, fed with sucrose solution, were released in the chamber. A belly shaven chick was kept tied inside the cage in immobilized condition.
The experimental chamber was tightly closed. Smoke toxicity was tested with commercial mosquito coils and herbal mosquito repellent from 15 min to 1 hr 30min intervals respectively (Vineeta et al. 2009).

Table 1 shows the comparative efficacy of Herbal mosquito repellent with commercial mosquito coil. The result obtained shows that during 6 to 7 pm, when no coils were used, the room was filled with mosquitoes. From 7 to 8 pm, a commercial coil was used to check the repellence activity in that area. It was shown that up to 95% of the mosquitoes were greatly reduced. When no coils were used from 8 to 9 pm again, numerous numbers of mosquitoes were gathered. After the burning of herbal mosquito repellent from 9 to 10 pm, it was shown that up to 85% of the mosquito number was greatly reduced. Table 2 shows the smoke toxicity effect of herbal mosquito repellent and commercial mosquito coil on C. quinquefasciatus. After 15 minutes, 54 mosquitoes dropped down and 20 mosquitoes died due to the burning of herbal mosquito repellent while 72 mosquitoes died with the application of commercial coil. The death of the mosquitoes increased with the application of the herbal mosquito repellent but as the time interval increased, 100 % the mosquitoes died with the application of the commercial coil.

Table 1 Comparative efficacy of Herbal mosquito repellent with commercial mosquito

Time (min) Type of Repellent Used Observed Results
6–7 pm No commercial coil Numerous mosquitoes
7–8 pm Commercial coil 100% of the mosquitoes were greatly reduced
8–9 pm No Commercial coil No: of mosquitoes increased greatly
9–10 pm Herbal mosquito repellent 85% of the mosquitoes were greatly reduced

A large number of essential oils extracted from different families have been shown to have high repellence against arthropod species. Among the essential oil producing plants, some genus such as Cymbopogon spp., Eucalyptus spp. and Ocimum spp. have been widely studied. Cymbopogon plants have been traditionally used to repel mosquitoes in jungle regions such as the Bolivian Amazon (Makhaik et al. 2005). This genus produces the most used natural repellents in the world (Trongtokit et al. 2005). Many extracts and essential oils isolated from these plants have been tested against different kinds of arthropods. Cymbopogon excavatus gave 100% repellence for 2 h, when it was evaluated in the laboratory against Anopheles arabiensis and its repellence decreased to 59.3% after 4 h (Mansour et al. 2000).
Essential oils belonging to plants in the citronella genus (Poaceae) are commonly used as ingredients of plant-based mosquito repellents. Cymbopogon citratus (lemongrass) belonging to the family Poaceae is a genus of about 55 species of grasses, native to warm temperate and tropical regions. Lemongrass oil is the essential oil obtained from the aerial part of Cymbopogon citratus. The plant has been widely recognized for its ethno botanical and medicinal usefulness (Tripathi et al.2009). Plant essential oils in general have been recognized as an important natural source of pesticides – insecticides, larvicides, and repellents.
Synthetic repellents tend to be more effective and/or longer lasting than "natural" repellents. However, some plant-based repellents may provide effective relief as well. Essential oil repellents can be short-lived in their effectiveness, since essential oils can evaporate completely. A test of various insect repellents by an independent consumer organization found that repellents containing DEET or picaridin are more effective than repellents with "natural" active ingredients. All the synthetics gave almost 100% repellency for the first 2 hours, where the natural repellent products were most effective for the first 30 to 60 minutes, and required reapplication to be effective over several hours. Research has also found that neem oil is mosquito repellent for up to 12 hours (Yap et al.1990). Citronella oil's mosquito repellency has also been verified by research, including effectiveness in repelling Aedes aegypti, but requires reapplication after 30 to 60 minutes.
Essential oils of many plants were observed to have mosquito repellent property and essential oils have received attention as potentially controlling vectors of mosquito borne disease (Trabouisi et al.2002). Therefore, the use of plant oils in insect/mosquito control is an alternative pest control method for minimizing the noxious effects of some pesticide compounds on the environment. Moreover the formulation is safe, eco-friendly, cheap, easy to use and has maximum repellence against mosquitoes. In addition these home-made herbal repellents are less harmful to our health than the coils available in the market. It can be prepared at home as it does not require any heavy infrastructure and investment as compared to coils and mats. It is evident from the present study that Lemongrass oil exhibit significant knock down activity at higher concentration. Further simulated and actual field trials required for commercialization of these herbal mosquito repellent.

To summarize, it is not only that Lemongrass oil showed good mosquito repellent activity in performed tests, but it is also strong mosquitocidal agent. Hence, Lemongrass essential oil, alone or in combinations with those obtained from other mosquito repellent plant species, could be potentially used for the preparation of mosquito repellent products. These could be in form of spray, cream, liquidator, coil, candle and sticks, and could be prepared using suitable carries/solvents/diluents, to get better protection from mosquito bites. Such formulations could help in reducing the harmful effects of synthetic mosquito repellents on human health. The oil formulations were found effective in controlling mosquito larvae in different breeding sites under natural field conditions. The results of this investigation indicate that the lemon grass oil could be beneficial for the control of vector borne diseases. It provides an herbal repellent with long lasting protection, safe for human life, human and domestic animal skin with no side effect and no feedback of environmental ill effect, as an alternative to synthetic chemical repellents.

Figure 1: Ingredients used for the preparation of Herbal Mosquito Repellent
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Figure 2: Machinery for the Manufacture of Mosquito Repellent

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