Bioactivity of Piper aduncum L. essential oil for insect pests of stored products1

ABSTRACT Determining the bioactivity of essential oils extracted from plants is crucial for the development of alternatives for controlling insect pests in stored grains. This study aimed to investigate the bioactivity of Piper aduncum L. essential oil for the control of Sitophilus zeamais (Coleoptera: Curculionidae), Sitophilus oryzae (Coleoptera: Curculionidae) and Cryptolestes ferrugineus (Coleoptera: Cucujidae). Bioassays were conducted to determine the oil toxicity, sublethal effects, attractiveness and flight initiation behavior. Toxicity tests were carried out to determine the lethal concentrations for 50 and 95 % of the insects (LC50 and LC95). Tests were also performed with sublethal exposures to C. ferrurineus, S. oryzae and S. zeamais, using their respective LC5 values (0.0002, 0.097 and 0.11 µL cm-2), to investigate effects on the attraction or repellency activity, as well as flight tests. C. ferrugineus showed greater LC50 (0.0005 µL cm-2) and LC95 (0.0012 µL cm-2) susceptibility, in relation to S. oryzae LC50 (0.35 µL cm-2) and LC95 (1.26 µL cm-2), and S. zeamais LC50 (0.39 µL cm-2) and LC95 (1.40 µL cm-2). The exposure to the sublethal LC5 concentration influenced the behavioral responses of attractiveness/repellency and flight activity. The oil had a neutral effect on C. ferrugineus LC5 (0.0002 µL cm-2) and an attractive effect on S. oryzae and S. zeamais LC5 (0.097 and 0.11 µL cm-2), and can be considered a potential insecticide for controlling pest weevil species of stored grains. RESUMO Determinar a bioatividade de óleos essenciais extraídos de plantas é primordial para o desenvolvimento de alternativas de controle de insetos-praga em grãos armazenados. Objetivou-se investigar a bioatividade do óleo essencial de Piper aduncum L. para o controle de Sitophilus zeamais (Coleoptera: Curculionidae), Sitophilus oryzae (Coleoptera: Curculionidae) e Cryptolestes ferrugineus (Coleoptera: Cucujidae). Foram realizados bioensaios para determinar a toxicidade do óleo, efeitos subletais, comportamento de atratividade e iniciação de voo. Testes de toxicidade foram realizados, determinando-se as concentrações letais para 50 e 95 % dos insetos (CL50 e CL95). Também foram realizados testes com exposições subletais para C. ferrurineus, S. oryzae e S. zeamais, utilizando-se as suas respectivas CL5 (0,0002; 0,097; e 0,11 µL cm-2), para averiguar efeitos na atividade de atração ou repelência, e testes de voo. C. ferrugineus apresentou maior susceptibilidade C