Efficacy and Safety of Essential Oils in The Control of Mosquito: A Review of Research Findings

For millennia, people have utilized essential oil-rich plants to control mosquitoes and other hematophagous insects. A review of the literature found that terpenoids and "sesquiterpenoid-rich oils" were effective in mosquito control. Due to the benign impression and successful prevention of mosquito bites, there has been a recent surge in the acceptance of biobased agents as mosquito control solutions, in conjunction with the worldwide demand to take action to battle climate change and its consequences. Materials for this review, which included works published for the last decade and even earlier, were sourced from the research databases Scopus, Web of Science, PubMed, ERIC, IEEE Xplore, ScienceDirect, Directory of Open Access Journals (DOAJ), and JSTOR using the keywords "essential oils," "larvicidal activity," "oviposition deterrent," "repellents," "toxicity," "safety," and "efficacy." " Recent research has found that low and middle-income African populations prefer plant-based repellents over manufactured chemical repellents such as N, N-diethyl-m-toluamide and N, N-diethyl phenylacetamide. Although ethnobotanical studies have demonstrated that biobased repellents are effective, environmentally friendly, and have almost no biohazard impact, they are also a source of bioactive substances for the creation of novel mosquito repellent products. The World Health Organization and other relevant agencies have yet to certify and accept the bulk of these plants with potential viability. Furthermore, there is a very limited comparison list of the efficiency and safety of these plant-based repellents. As a result, there is a need to further investigate these bio-based natural repellents and their formulations for successful mosquito control, allowing for the production of novel repellents that deliver high repellence while also ensuring consumer safety.


Introduction
Mosquitoes pose a significant threat to millions of people worldwide, vectoring diseases such as malaria, dengue fever, yellow fever, filariasis, Japanese encephalitis, and Zika virus (Benelli & Mehlhorn, 2016;Patula et al. 2016;Saxena et al. 2016) which cause widespread morbidity, mortality and significant economic burden (Nyawira et al. 2020). Malaria is the most serious risk factor, and it is caused by Plasmodium falciparum, which is carried by female Anopheles mosquitos. There are around 3500 mosquito species throughout the tropical and subtropical regions of the world (Prabakaran et al. 2017).
Dengue fever is a viral virus that slowly spread over the Western Hemisphere, grew more aggressively in the 1990s, and is mostly vectored by Aedes mosquitos (Aedes aegypti and, to a lesser degree, Aedes albopictus). Dengue fever instances are underreported, and many cases are misclassified. Dengue viruses pose a threat to about 390 million individuals in 128 countries (Beatty, 2007). Recent outbreaks of Zika virus infections in South America, Central America, and the Caribbean (Sujitha et al., 2015) reflect the most recent arrivals of the Western Hemisphere's four arboviruses, dengue, West Nile virus, and chikungunya (Benelli & Mehlhorn, 2016;Fauci & Morens, 2016;Musso & Gubler, 2016). Unfortunately, there is no current therapy for the majority of arboviruses transmitted by mosquitoes, particularly the dengue and Zika viruses (Sujitha et al., 2015).
Yellow fever is a viral hemorrhagic illness that is prevalent in tropical Africa, and Central and South America. It is spread by Aedes aegypti. Few individuals who get the virus experience severe symptoms, and around half of those infected die within 7-10 days. Yellow fever may be avoided with a very efficient, safe, and inexpensive vaccination. Within 30 days, the vaccine delivers effective protection in 99 % of immunized individuals (Katia, 2021).
Malaria, particularly P. falciparum infections, is a serious public health concern in underdeveloped nations such as Nigeria. Malaria morbidity and death influenced economic growth. Attempts to control or eliminate the illness, however, have mostly failed due to the rise of insecticide-resistant vectors and drug-resistant strains caused by P. falciparum kelch13 gene (PfKelch13) mutations (Amaratunga et al., 2019). A global effort has always been and will continue to be made to use plants for disease prevention, vector control, and treatment where the traditional method is unsuccessful, costly, and unaffordable. The hunt for plant essential oils (EOs) as bio-insecticides for mosquito control is commonly thought to be a viable alternative to synthetic ones. According to research data available in the literature, essential oils from plant origins are used as mosquito repellants with high efficacy in terms of protection period and mortality rate of the vector species (Kweka et al., 2008;Ghosh et al., 2012).
Toxicology, on the other hand, is a major concern for the skin, neurological, and immune systems of humans and other animal species (Choochote et al, 2007). Despite the claimed effectiveness of synthetic insecticides with long-lasting, it has however been implicated to exhibiting toxicity concerns resulting in skin irritation and breathing difficulties. However, EOs derived from plants, like lemon, are less hazardous than synthetic repellants (Nerio et al., 2010). Essential oils from plants such as Eucalyptus camaldulensis, Nepeta cataria, and Vitex negundo have been shown to exhibit strong mosquito-repellent properties (Asadollahi et al, 2019;Huang et al., 2012;Patience et al,. 2018;Mohammadi & Saharkhiz, 2011;Moudachirou et al., 1999;Singh et al., 2011) with very low toxicity. The effectiveness and safety of EOs as mosquito larvicides, repellents, and oviposition deterrents, as well as the toxicity of EOs on non-target species, are the subject of this review.

Conventional Methods for Mosquito Control
There is rising awareness about the negative consequences of mosquito control compounds using synthetic insecticides which have led to a greater desire to seek natural and ecologically friendly insect repellants (Singh et al., 2011). The use of repellents to protect humans from mosquito bites has previously been recognized as a crucial component of a fully integrated insect-borne disease control program (Amer & Mehlhorn, 2006). Commercial synthetic repellents frequently contain chemicals such as N, N-diethyl-meta-toluamide (DEET), Allethrin, N, N-diethyl mandelic acid amide, and dimethyl phthalate (Asadollahi et al, 2019). These chemical repellents are hazardous to public health and should be avoided due to their negative effects on synthetic fabric and plastic, as well as toxic reactions such as allergy, dermatitis, and cardiovascular and neurological side effects that have been reported following widespread misuse and regular usage (Govindarajan et al., 2016). The increased and constant use of synthetic repellents for mosquito control has disrupted natural ecosystems, resulting in pesticide resistance, mosquito population resurgence, and negative effects on non-target species (Govindarajan et al., 2016;Sanghong et al,.2015). As a result, employing natural mosquito repellent as an alternative to new synthetic repellents should be a cooperative option to reduce the negative impacts on the environment and human health.

Synergistic Action of Essential Oils
In terms of pesticide action, the goal of designing synergistic combinations is to minimize the dose of potentially polluting compounds while also lowering the possibility of resistance development. The ethnic-repellent formulation allows for the employment of a diverse variety of pest-repellent materials, such as plant extracts, fermentation products, and commercial clay and rock powder products. Nonetheless, due to the commercialization of standardized industrial items, the use of handmade products has diminished in recent years (Kyotosh, 2005). Also, it was discovered that combining extracts of Azadirachta indica, Khya senegalensis, and Hyptis suaveolens with conventional insecticides at one-half the recommended rate reduced cotton damage caused by the Helicoverpa armigera (bollworm), and provided greater efficacy than the conventional product alone at their recommended rate (Sinzogan et al. 2006). This led to an increase in farmers' confidence in indigenous technologies as a result of such a direct demonstration of the usability and value of botanical treatments (Chorianopoulos et al. 2006;Kithva, 2009).
The synergistic thinking that underpins the usage of combination products aims to create a dynamic product with several modes of action while maintaining the concept that the combined product's effect is greater than the sum of its known and unknown chemical components and should be optimized. The positive and negative synergy between the essential oil or its components and the other substances in the mix might occur (Harris, 2002). This is a crucial consideration since EOs may create a synergy that is subsequently nullified by the base product. The pH and salinity of the base may affect the activity of the EO. It has been observed that a low pH and salty environment may boost the formula's overall repellent activity (Chorianopoulos et al., 2006). Synergistic effects have been demonstrated for EO combinations such as thyme, Their composition can vary greatly across aromatic plant species and variations, as well as between geographical locations within the same variety (Juliani et al., 2007). The oils are mostly utilized in the perfume business, but some are also used in the food sector to make pharmaceuticals, soaps, shampoos, cosmetics, paints, and so on. Aside from the purposes described above, research has revealed that certain EOs have antibacterial and antifungal properties against specific pathogenic organisms, making them helpful in the pharmaceutical business (DeLisser et al., 1997;Bennasir & Sridhar, 2012). The yield of EOs is inherently limited, ranging from 0.5 to 6% by weight (except clove buds, which produce 11-15 %) (Jones, 1994). Further, E. camaldulensis, N. cataria, and V. negundo with EO yields of 5.9 %v/w, 4.7 %v/w, and 1.0 %v/w, respectively, have been found to exhibit substantial mosquito-repellent potential (Asadollahi et al. 2019;Patienceet al. 2018;Moudachirou et al. 1999;Hebbalkar et al. 1992;Mohammadi & Saharkhiz, 2011;Singh et al. 2015).

Repellant Activity of Essential Oils
Repellants are compounds that keep insects from flying or biting humans or animals. Some monoterpenes, such as cineole, α-pinene, eugenol, limonene, terpinolene, citronellol, cineole, citronellal, thymol, and camphor, are frequent components of many EOs that have been found to have mosquito repellent properties (Yang et al. 2003;Vongsombath et al. 2012;Park, 2005). β-caryophyllene is the most commonly referenced sesquiterpene as a powerful repellent against Aedes aegypti (Gillij et al. 2007). Even though the presence of monoterpenoids and sesquiterpenes appears to be related to the repellent properties of several EO (Vongsombath et al. 2012;Ravi & Sita, 2007;Sukumar et al., 1991;Hassanali, 2005. Luo et al.,2022 observed that phytol had a strong repellant effect on Anopheles Sinensis. Toloza et al. (2006) investigated the repellent efficacy of 16 essential oils derived from indigenous and exotic Argentine plants, as well as 21 isolated secondary metabolites, and reported that benzyl alcohol, menthol, and thymol were the most effective against Pediculus humanus capitis. Furthermore, the tick's repellent properties of α-pinene, β-citronellol, geraniol, and cinnamyl alcohol extracted from Dianthus Calophyllumm essential oil are effective in controlling ticks on animals. Odalo et al. (2005) and Omolo et al. (2004) studied the repellent properties of 12 Kenyan plants from various genera against A. gambiae, as well as some metabolites isolated from these plants. The most efficient repellent substances were perillaldehyde, cis-verbenol, cis-carveol, myrcene, citronellal, perillyl alcohol, caryophyllene oxide, thymol, 3-carene, carvacrol, 4-isopropylbenzenemethanol, and geraniol. Sesquiterpenoid, diterpenoid, acyclic, monocyclic, and bicyclic monoterpenoids are among the many structural kinds.
Previous research has shown that terpenoids with two functional groups are physiologically efficacious as mosquito repellents (Han, 2008;Hazarika et al., 2022). Although the repellent effect of EOs is often attributed to specific molecules, some synergistic interactions among these metabolites may result in greater bioactivity than the single isolated components (Gillij et al. 2007;Omolo et al. 2004;Hummelbrunner & Isman, 2001). The repellant efficacy of a blend of EOs from Artemisia princeps and Cinnamomum camphora against adults of Sitophillus oryzae L. and Bruchus rugimanus was much greater than that of individual oils (Liu et al. 2006).

Improvement of Essential Oil Repellence Efficiency
Although essential oils are useful when applied freshly, their protective benefits generally wear off soon (Trongtokit et al. 2005). In the case of mosquitoes, essential oils often function in the vapor phase, which is only effective for a limited length of time. This is most likely due to their high volatility, which might be reduced by developing formulations that can maintain active chemicals on the skin for extended periods. The increase in repellence activity for EOs is heavily influenced by the product content.
Creams, polymer mixes, or microcapsules-based formulations for controlled release and improved repellency duration (Trongtokit et al., 2005;Yuan & Ping Hu, 2011;Sharma & Ansari, 1994;Nentwig, 2003;Chang et al. 2020) have been developed using nanotechnology. For example, to boost mosquito-repellent characteristics, Zanthoxylum limoncello oil was effectively microencapsulated in glutaraldehyde cross-linked gelatin (a polymer) (Maji et al., 2007). The efficiency of a product in a topical application containing citrus oil in repelling mosquitos was evaluated on various formulations. The order of efficacy was hydrophilic base > emulsion base > oleaginous base (Oyedele et al. 2002). To increase the efficiency of the EO repellent, fixative elements such as liquid paraffin (Oyedele et al. 2002) vanillin (Tawatsin et al. 2001), salicylic acid (Blackwell et al, 2003), mustard, and coconut oils were used. Vanillin is a common chemical that is combined with EO (Choochote et al.,2007;Tawatsin et al. 2001;Chaithong et al.2006). This chemical greatly boosts the protection times of EO, particularly when used against A. aegypti (Sritabutra & Soonwera, 2013), it has also been shown to function effectively with other mosquito species. When looking for techniques to improve the repellency of essential oils, many variables should be considered: new formulations, fixative additives, nanoencapsulation, and the manufacture of combination repellents are all potential for increasing the effectiveness and economic value of repellents generated from essential oils.

Larvicidal Activity and Safety of Plant Essential Oils
Plants and phytophagous insects have been in conflict for millennia, which has resulted in the selection of a multitude of secondary metabolites with insecticidal action across a wide variety of plant species. It is hardly unexpected, then, that EOs have an immediate toxic impact on mosquito larvae when given to water in a controlled laboratory context. According to Romi et al. (2003), the LC 50 of temephos on larvae of Aedes albopictus Skuse populations in Italy varied from 0.0026 to 0.0085 ppm, but the LC 50 of Bti for field-collected strains of A. aegypti differs.
Few EOs have LC 50 < 1 ppm and multiple investigations have revealed that more than 50 ppm is necessary to kill 50% of the larvae studied (Shaalan et al,. 2005;Dias & Moraes., 2014;Pavela, 2015). According to WHO recommendations, such high concentrations are impractical. Shaalan et al.(2005) suggested that extracts generating less than 100% larval death in laboratory circumstances at a dosage of 10 ppm be stopped. In addition to mosquito larvae activity, concerns of practicability must be addressed. Aside from mosquito larvae activity, problems of practicability must be addressed.
Products based on essential oils should be useful in several conditions such as organic matter in the water, salinity, temperature, pH, etc. The different degrees of vulnerability among mosquito species must also be considered.
The insecticidal effect of essential oils on mosquito larvae has sparked considerable attention in recent scientific literature, with numerous studies envisioning EOs as possible alternatives to conventional larvicides (Masetti, 2016). Larval control is an important strategy in the integrated management of most mosquito species (Becker et al., 2010), and numerous pesticides have been employed to eradicate mosquito larvae. In general, poorer nations apply less stringent regulatory limits (Blä sing et al., 2012), but the relatively high cost of traditional larvicides, as well as the difficulty in obtaining such goods, impede larval control initiatives. For these reasons, there is a significant deal of interest in the development of novel larvicides that do not harm human health or aquatic habitats and should be freely accessible and cheap in underdeveloped nations. As a result, EOs have regained popularity as prospective low-risk pesticides (Hummelbrunner & Isman, 2001;Regnault-Roger et al., 2012). Terpenoids and, to a lesser degree, phenylpropanoids are the most common elements of EOs (Bakkali et al, 2008). Several reports have been reported on EOs from a wide range of plant species that show an insecticidal effect on mosquito larvae by either the whole extract or specific purified components (Shaalan et al. 2005;Pavela, 2015;Hunter et al.1996;Liu et al. 2019). Aside from effectiveness, most research indicated that EOs had no influence on human health and have no environmental negative effects (Bhavaniramya et al. 2019;Maurya, A., et al. 2021;Okon et al.2021).

Health Impact of Essential Oils
Many popular EOs and their primary components have been examined experimentally for a long time as additives for foods and drinks, perfumes for cosmetics, and pharmaceutical items (Hummelbrunner & Isman , 2001). In general, these EOs are not hazardous to mammals or other vertebrates when consumed orally (Regnault-Roger & Vincent, 2012;Trumble, 2002). Aside from contact dermatitis and allergic reactions caused by repeated skin applications of Melaleuca alternifolia (Maiden Betcher). Some EOs such as Mentha pulegium L., Artemisia absinthium L., and Hedeoma pulegiides (L.) Pers. can cause severe acute poisoning (Trumble, 2002). If probable larvicidal activity is discovered for an EO for which no health issues have previously been identified, mammalian toxicity testing should be done. Such testing should be necessary before the start of any field trials.  Table 2, showed some major chemical constituents and biological activity of essential oils isolated from plants. The complexity of essential oils chemical constituents isolated from plants which work in synergy may impact positively on the health of human, animals and organisms. The chemical constituents in these essential oils dominated by monoterpenes (oxygenated and hydrocarbons), accounted for 82.8% of the oil's content possessing antifungal, bactericidal, pesticidal, trypanocides, antimicrobial, antioxidant activities which promote good health and used for various medical applications. With the emergence of conventional drugs for the treatment of microbial resistance, and viral infections essential oils have shown to have potentials as alternative to these conventional drugs in the management of the emergence of microbial resistance, viral infections crop protection amongst others. Essential oil constituents have been implicated in possessing bactericidal, virucidal, and fungicidal activity in clinical trials (Deyno et al.;Valdivieso-Ugarte et al. 2019). As a result of these biological activities of these essential oils, it is suggested that it might not just be used to fight infections, but also can play a role in the preservation of food due to their antimicrobial activity combined with their antioxidant property (Deyno et al.;Valdivieso-Ugarte et al. 2019).
Insect-repellent and Larvicidal activity of mosquito-borne diseases such as dengue fever, yellow fever, malaria, filariasis, and viral encephalitis affect large human populations. The bite causes serious allergy such as local skin reaction, and systemic reaction. Essential oils of H. suaveolens have shown larvicidal activity against yellow fever mosquito Aedes aegypti (L), and Aedes albopictus larvae. The larvicidal activity of the essential oils is due to the chemical constituents such as alpha-pinene, beta-pinene, sabinene, terpinolene, beta-caryophyllene, and 4-terpineol (Barbara et al. 2012) in the plant. Literature available on the scientific data of the biological activity of essential oils has demonstrated that they have contact and fumigant toxicity to a number of economically important insect and mite pests, as well as to plant pathogenic fungi. EOs have impact on human health in different ways. Many studies available in the literature has shown the essential oils to possess psychological effects for example, in reducing anxiety, treating depression, and aiding falling asleep. The essential oils have also been shown to possess antimicrobial, antiviral, antioxidant, anti-inflammatory properties and used as an alternative to synthetic insect repellents. As there are many proven health benefits to essential oils, there are also adverse effects. Altogether, there has been a great number of research investigations on the essential oil applications in health however, their complex chemical components and the spectrum of possible biological activities require more research findings on their true effects on human health,

Environmental Impact
One of the most appealing advantages of EOs over traditional synthetic pesticides is their low environmental persistence and lack of accumulation in food chains (Hummelbrunner & Isman, 2001). Several studies on the impact of EOs on aquatic biocoenosis have been reported. Most of these investigations, however, utilized fish as non-target creatures (Govindarajan, 2016;Pavela & Govindarajan, 2004), with arthropods being seldom examined. In general, EOs are neurotoxic contact insecticides that target γ-Aminobutyric acid and octopamine synapses as well as acetylcholinesterase (Regnault-Roger et al. 2012). Due to the existence of these molecular targets in all arthropods, there are low odds of finding a significant degree of EO selectivity in non-targeted arthropods. EOs of Piper klotzschianum (Kunth) DC were found to have similar LC 50 values with Artemia salina L. nauplii and Aedes aegypti larvae (Sarmento-Neto, et al.2016).
Toxic effects of EOs and their components isolated from the Myrtaceae have also been observed in laboratory trials against Daphnia Magna Straus (Park et al. 2005). EOs from Pinus kesiya Royle ex Gordon, on the other hand, were generally nontoxic to Rhynchota Notonectidae (water bugs) (Govindarajan et al. 2017). On tested mosquito larvae, however, these extracts had LC 50 values greater than 50 ppm. Except for microbial larvicides, all other pesticides used to control mosquito larvae (IGRs, diflubenzuron, temephos, and pyrethroids) have been found to harm non-target aquatic insects and crustaceans (Pisa et al 2014;Suchismita & Anilava, 2008;Lacey, 2007). EOs appear to lack selectivity in the amounts necessary to be effective on mosquito larvae. However, because EOs have a shorter environmental persistence, the final impact of EOs on non-target arthropods under real-world settings is anticipated to be smaller than that of chemical larvicides.

Insecticidal Activity and Safety of Plant Essential Oils
The majority of monoterpenes are cytotoxic to animal and plant tissue, reducing the number of undamaged Golgi bodies and mitochondria, decreasing cell membrane permeability, and interfering with respiration and photosynthesis (Stefano et al. 2015). They're also very flammable, and many of them serve as chemical messengers for insects and other animals. The EO quantities needed to remove insect pests, as well as their mechanisms of action, may have consequences for human and other vertebrate safety. Even though little is known about the physiological effects of EOs on insects, treatments with specific EOs or their components elicit symptoms that imply a neurotoxic mechanism of action. (Kostyukovsky et al. 2002;Shaaya et al. 1997). Linalool, a monoterpenoid, has been demonstrated to alter the neurological system in insects, influencing ion transport and the release of acetylcholine esterase (Rajashekar et al.2014). In insects, octopine performs several biological activities, including those of a neurotransmitter, neurohormone, and circulating neurohormone-neuromodulator (Magee et al. 1984;Orchard, 1982). Based on pharmacological criteria, octopamine operates by engaging with at least two types of receptors known as octopamine-1 and octopamine-2 (Kastner et al. 2014).
Interrupting the octopamine function causes a complete collapse of the nervous system in insects. As a result, the insect octopaminergic system is a bio-rational target for pest control. The absence of octopamine receptors in vertebrates is most likely responsible for EO's strong mammalian selectivity as insecticides. Some EO compounds have been shown to act on insects' octopaminergic systems (Jankowska et al. 2018). Cloned cells from the brains of Periplaneta americana and Drosophila melanogaster (Enan, 2005) demonstrated that eugenol mirrored octopamine in elevating intracellular calcium levels. It was also established that octopamine receptors play a role in this. Furthermore, eugenol toxicity was increased in mutant Drosophila melanogaster missing octopamine synthesis, showing that the toxicity is mediated through the octopaminergic system, although geraniol toxicity was not. It has been proposed that the insecticidal activities of eugenol are due to the cellular alterations generated by it ). Kostyukovsky et al. (2002 discovered a similar result, suggesting that EO components may compete for octopaminergic receptor activation; they showed significant effects at low dosages in Helicoverpa armigera abdominal epidermal tissue ).

Oviposition Deterrence and Safety of Essential Oils
Ovicides are chemicals that prevent insect pests from laying eggs. EOs derived from natural plants or nano-encapsulated EOs have been found to significantly reduce the number of eggs laid by insect pests such as Bemisia tabaci (Fortes et al. 2020;Younas et al.2021). A study was carried out on Bemisia tabaci utilizing nano-encapsulated EO from the Clematis aromatic plant. The findings showed that EOs might potentially inhibit the egg production of B. tabaci in common bean leaves (Peres et al. 2013). The efficiency was 98%, and the concentration of the EO released from the nanocapsule increased. Essential oils from Thymus Vulgaris, Pogostemon cablin, and Corymbia citriodora significantly decreased oviposition, egg hatching, and nymph survival (Yang et al. 2003). The three essential oils from the plants reduced egg hatching by 50%, according to the findings. The oils caused development to be disrupted in certain eggs of the B. tabaci bug. Nonetheless, there is no experiment on the oviposition deterrence of EOs on mosquito vectors found in the literature. As a result, further research into mosquitoes and the oil's safety impact on non-target creatures is required.

Essential Oils Trends and Development
A review of recent essential oil patents indicated that the great majority of the advances were centered on home uses. Some patents are also related to domestic animal protection. A great number of patents have been awarded for the protection of garments against moths and beetles. EOs have been used in agriculture and the food sector, in addition to these home purposes. Essential oils have also been demonstrated to be beneficial in the manufacture of products. Eucalyptus EOs, pyrethroids, and borax were combined in a wood preservation solution (Urabe, 1992). By thoroughly impregnating the polymer layer with Thujopsis dolobrata EO, the insect resistance of veneer-faced panels is enhanced (Akita et al. 1991;Sugimoto & Tsubochi, 1992). All of these examples highlight the adaptability of EOs in a variety of circumstances. Cockroaches, mosquitoes, mites, ticks, and other household insects are repelled by a bio-rational repellent based on nepetalactone and dihydro-nepetalactone from N. cataria (Hazarika et al. 2012;Scialdone & Liauw, 2008). Tetrahydronootkatone and 1,10-dihydro nootkatone, both derived from Chrysopogon zizanioides oil, have been patented as mosquito, cockroach, termite, and ant repellents (Baton et al. 2005;Henderson et al. 2005). Thyme oil, as well as monoterpenoid combinations such as thymol, anethole, eugenol, and citronellal, have all been trademarked for pesticide action against cockroaches and green peach aphids. Similarly, human louse insecticides, citronellal, citronellol, citronellyl, or a mixture of these have been patented Sritabutra & Soonwera, 2013).

Conclusion
The interest in developing plant herbs as an alternative to chemical insecticides has been piqued due to their ease of availability, low cost, and lower environmental impact. Numerous ethnobotanical studies have found that plants can be used as an alternative source of mosquito control measures. They have a long history of use in many parts of the world. Natural products are thought to be safer for human consumption than synthetic compounds. Furthermore, unlike synthetic repellents, which are harmful to the environment, lethal effects on non-target organisms and mosquito resistance to insecticides have increased over the last five decades. These issues have highlighted the need for alternative strategies to be developed.
This research examined the efficacy and safety of essential oil-rich plants used for mosquito control from a range of sources. Based on the research gaps discovered in the literature, it is, therefore, recommended that researchers, scientists, and educators to examine the mechanisms involved in how the interactions of the components of each essential oil result in increased repellent ability (for the synergistic phenomenon). More study on the effects of EOs on other aquatic arthropods that prey on mosquito larvae, such as dragonfly nymphs and water beetles, is also required. Despite the widespread usage of plants as repellents, scientific understanding of these plants is limited, necessitating the initial step of collecting ethnobotanical data on these species.