Contents lists available at ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro Essential oil of Lippia sidoides and its major compound thymol: Toxicity and walking response of populations of Sitophilus zeamais (Coleoptera: Curculionidae) Alexandre P. Oliveira a , Abraão A. Santos a,c , Alisson S. Santana a , Ana Paula S. Lima a , Carlisson R. Melo a , Emile D.R. Santana a , Taís S. Sampaio a , Arie F. Blank a , Ana Paula A. Araújo b , Paulo F. Cristaldo a , Leandro Bacci a,* a Departamento de Engenharia Agronômica, Universidade Federal de Sergipe, Cidade Universitária Professor José Aloísio de Campos, Avenida Marechal Rondon s/n, Rosa Elze, 49100-000, São Cristóvão, Sergipe, Brazil b Departamento de Ecologia, Universidade Federal de Sergipe, Cidade Universitária Professor José Aloísio de Campos, Avenida Marechal Rondon s/n, Rosa Elze, 49100- 000, São Cristóvão, Sergipe, Brazil c Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil ARTICLE INFO Keywords: Alternative control Insect resistance Terpenes Verbenaceae ABSTRACT The maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae), is the main pest of stored grains across tropical regions. An alternative strategy to the use of synthetic insecticides for the management of S. zeamais is the development of botanical insecticides based in the essential oils (EOs) from aromatic plants. In the present study, we evaluated the lethal and sublethal effects of the EO of Lippia sidoides (Cham.) and its major compounds (thymol and ρ-cymene) on different populations of S. zeamais. For this, we determined toxicity by fumigation of treatments of five populations from different Brazilian regions and assessed the lethal time and walking behavior for the most tolerant and susceptible populations. The lethal concentration required to kill 50% of S. zeamais populations ranged from 35.48 to 118.29 μLL -1 air for EO of L. sidoides, 65.00–91.23 μLL -1 air for thymol and 801.24 to 2188,83 μLL -1 air for ρ-cymene. Population from Jacarezinho was the most tol- erant to treatments, while population of Rio Branco was the most susceptible one. The survival of S. zeamais populations was significantly affected by treatments and ρ-cymene showed the faster action on both Jacarezinho and Rio Branco populations (LT 50 = 0.3 h). The walking behavior of maize weevil showed that the EO of L. sidoides and thymol present repellent effect, however, ρ-cymene present attractive effect. Therefore, the EO of L. sidoides and its major compound thymol are promising source to develop bioinsecticides for the management of S. zeamais populations with different levels of resistance. 1. Introduction In recent years, resistance to insecticides and concerns about the risks of synthetic insecticides to non-target organisms, environment and human health have driven the search for alternative methods of con- trolling insect pests. Essential oils (EOs) from aromatic plants have been considered a safe alternative strategy to manage insect pests, including those of stored products (Isman, 2006; Santos et al., 2011). The EOs from plants are complex mixtures with large numbers of volatile organic compounds (mono- and sesquiterpenes) that can be extracted from seeds, stems, leaves and flowers and which can exhibit bioactivity on a variety of insects. The efficiency of EO for insect control is, in large part, due to its complexity and the potential for additive or synergistic effects among its compounds. Advantages of using EO compounds in pest management compared to synthetic insecticides include a potential decrease of resistance development due to the mixing of compounds acting at various sites of action and the low persistence in the environment due to high volatile of compounds, and therefore lower toxicity to non-target organisms (Correa et al., 2015; Peixoto et al., 2015; Tak et al., 2016a). The maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae), is considered the most destructive insect pest of stored https://doi.org/10.1016/j.cropro.2018.05.011 Received 8 March 2018; Received in revised form 10 May 2018; Accepted 12 May 2018 * Corresponding author. E-mail addresses: tande1992@gmail.com (A.P. Oliveira), abraaoufs@gmail.com (A.A. Santos), alisson.0910.silva@gmail.com (A.S. Santana), ana.lima9a@gmail.com (A.P.S. Lima), carlisson_melo@hotmail.com (C.R. Melo), emiledayara23@gmail.com (E.D.R. Santana), tais.parker@gmail.com (T.S. Sampaio), afblank@ufs.br (A.F. Blank), anatermes@gmail.com (A.P.A. Araújo), pfellipec@gmail.com (P.F. Cristaldo), bacci.ufs@gmail.com (L. Bacci). Crop Protection 112 (2018) 33–38 0261-2194/ © 2018 Published by Elsevier Ltd. T