The objective of this work was to evaluate the contact toxicity of essential oil of Croton pulegiodorus Baill on six populations of Sitophilus zeamais Motschulsky. The S. zeamais populations used were from Crixás-GO, Espírito Santo do Pinhal-SP, Juiz de Fora-MG, Picos-PI, Serra Talhada-PE, and Vicentina-MS, Brazil, and present different susceptibility to synthetic insecticides. The essential oil of C. pulegiodorus used was obtained from plants collected in Triunfo-PE, Brazil. The lethal concentrations (LC50 and LC90), toxicity ratio of the essential oil, and the resistance ratio of the populations were estimated. The S. zeamais population from Serra Talhada-PE presented the lowest LC50 (4.21 μL 20 g-1) and LC90 (6.67 μL 20 g-1) and was the reference for susceptibility to the essential oil of C. pulegiodorus. The S. zeamais population from Espírito Santo do Pinhal-SP presented the highest LC50 (6.02 μL 20 g-1) and LC90 (10.55 μL 20 g-1) and was the reference for tolerance to the essential oil of C. pulegiodorus. The toxicity ratio ranged from 1.01 (Picos-PI) to 1.43 (Serra Talhada-PE); and the resistance ratio ranged from 1.13 (Crixás-GO) to 1.43 (Espírito Santo do Pinhal-SP). The essential oil of C. pulegiodorus reduced the emergence of adult S. zemais and showed residual effect, with contact toxicity, after 30 and 60 days of application.
O feijão-caupi, Vigna unguiculata, possui um importante papel na alimentação. No entanto, essa cultura ainda sofre grandes perdas devido ao ataque de insetos-praga, sendo fundamental o desenvolvimento de métodos de manejo para garantir o controle de Callosobruchus maculatus (Coleoptera: Chrysomelidae). Foi avaliada a toxicidade, por contato, a taxa de oviposição e emergência de C. maculatus em grãos de feijão-caupi tratados com o óleo essencial de Croton blanchetianus e o efeito residual em diferentes períodos de armazenamento, sendo, ainda, determinadas as concentrações letais (CL50 e CL90). O teste de toxicidade por contato e taxas de oviposição e emergência de C. maculatus foi realizado em placas de Petri, utilizando 6 concentrações (0; 2.5; 5; 7.5; 10 e 12.5 μL/20g). No teste residual, os grãos foram submetidos a diferentes períodos de armazenamento (0, 30 e 60 dias). Os resultados mostraram que o óleo essencial de C. blanchetianus apresentou toxicidade por contato sobre C. maculatus. Observou-se que as concentrações letais foram consideradas baixas. Este óleo também reduziu a oviposição e emergência de adultos. Por outro lado, durante diferentes períodos de armazenamento o óleo teve sua ação diminuída, apresentando potencial para ser utilizado em programas de manejo de C. maculatus em feijão armazenado.
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