Contents lists available at ScienceDirect Ecotoxicology and Environmental Safety journal homepage: www.elsevier.com/locate/ecoenv Larvicidal activity of selected essential oil in synergized combinations against Aedes aegypti G. Navaneetha Pandiyan, Nisha Mathew ⁎ , Sundharesan Munusamy ICMR-Vector Control Research Centre, Puducherry 605006, India. ARTICLE INFO Keywords: Aedes aegypti Essential oil Trachyspermum ammi Illicium verum Syzygium aromaticum Mosquito Larvicide Synergism ABSTRACT This study was conducted to attain an alternate plant essential oil (EO) based mosquito larvicide against the dengue vector Aedes aegypti. Here three plants were selected based on their local availability, safety and in- secticidal properties. EOs were extracted from Syzygium aromaticum (Myrtaceae) flower buds, fruits of Illicium verum (Schisandraceae) and Trachyspermum ammi (Apiaceae) by hydro-distillation and tested against Ae. aegypti larvae individually and in combinations to find synergistic interactions. Chemical constituent analysis of EOs was done by GC/MS/MS analysis and the main constituents in T. ammi were thymol (93.58%) and terpinen-4-ol (2.16%), in S. aromaticum eugenol 56.32% and caryophyllene 17.91% and in I. verum trans-anethole 53.05% and p-anisaldehyde 12.47%. The EOs from T. ammi, I. verum and S. aromaticum and their top components thymol, trans-anethole and eugenol exhibited larvicidal activity with LC 50 values 39.48, 41.30, 66.90, 59.76, 50.19 and 60.89 mgL -1 respectively against Ae. aegypti larvae. The values for the co-toxicity factors for the binary com- binations of the EOs were > 20 showing synergistic interactions among the binary mixtures. The respective LC 50 values for the 1:1 binary combinations (S. aromaticum + I. verum), (S. aromaticum + T. ammi) and (I. verum + T. ammi) were 49.07, 48.54 and 27.67 mgL -1 . β-cyclodextrin inclusion complex made with I. verum + T. ammi combination showed an LC 50 value of 23.93 mgL -1 . On the whole the outcome of this study draw attention to the capability of synergistic EO combinations to emerge as a safe and environment friendly effective larvicide to control Aedes mosquitoes. 1. Introduction The globalization of the vector borne viral diseases such as dengue, chikungunya and Zika viral infection were due to the widespread pre- sence of Aedes vectors in many parts of the world and the increased human travel that helped geographic distribution. Aedes proliferation is difficult to predict, but could be restricted by way of appropriate pre- cautionary measures (Imperato, 2016). Among these, dengue is con- sidered as the most predominant and quickly spreading mosquito-borne viral disease of human beings (Guzman and Harris, 2015). Dengue is spread by Aedes aegypti mosquito that breeds in peri-do- mestic clean water shelters inside and outside the house (Benelli and Mehlhorn, 2016). Adult Ae. aegypti female mosquitoes are extremely anthropophilic in character and make use of man-made water storage places for egg laying and raising the immature stages of its biphasic life cycle. Dengue viral infection is a very serious mosquito borne disease commonly seen in tropic regions (Cui et al., 2018). Recently, numerous dengue fever occurrences have been reported from India and other countries (Shrivastava et al., 2018; Veerasekar and Swaminathan, 2017). In India co-circulation of more than one dengue virus serotypes have been reported (Shrivastava et al., 2018). Vector control with synthetic larvicides to target the larvae in mosquito breeding places stands as one of the key approaches for accomplishing mosquito vector management (Dusfour et al., 2011). The inadequacy of the control plans (Medronho, 2008) and vector mosquitoes becoming resistant to syn- thetic insecticides have played a major part towards outbreaks (Beserra et al., 2007; Braga et al., 2004). Besides, unfavorable consequences due to the application of synthetic chemical insect controlling agents on the environment also have encouraged the exploration for alternative tox- icologically safe, eco-friendly larvicide, such as botanical insecticides. Earlier work on phytochemicals as insecticides and repellents against mosquitoes were found promising and encouraged us to work further on the development of botanical insecticides (Pavela et al., 2018; Irrusappan and Nisha, 2018; Kamaraj et al., 2018; Lalthazuali and Nisha, 2017; Govindarajan and Benelli, 2016; Pavela, 2015; Samidurai and Nisha, 2014; Vidhya and Nisha, 2014; Nisha et al., 2009; Amer and Mehlhorn, 2006). Essential oil consists of mixtures of volatile chemical constituents https://doi.org/10.1016/j.ecoenv.2019.03.019 Received 17 November 2018; Received in revised form 3 March 2019; Accepted 4 March 2019 ⁎ Corresponding author. E-mail address: nishamathew@yahoo.com (N. Mathew). Ecotoxicology and Environmental Safety 174 (2019) 549–556 0147-6513/ © 2019 Elsevier Inc. All rights reserved. T