Toxicidade do óleo essencial de mostarda sobre populações de Sitophilus zeamais

• Autor(a) principal: Freitas, Rita Cristina Pereira de
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/3927
• topic: Comportamento; Isotiocianato alilo (ITCA); Inseto; Toxicologia; Behavior; Allyl isothiocyanate (ITCA); Insect; Toxicology; CNPQ::CIENCIAS BIOLOGICAS

The aim of this study was to evaluate the toxicity of the essential oil of mustard (EOM) for adults of five populations of Sitophilus zeamais (Coleoptera: Curculionidae) and the influence of the essential oil on the locomotory behavior of the populations. EOM was used with 90% of allyl isothiocyanate volatile component (ITCA), diluted in soybean oil at 1:9 v/v to obtain a 9% solution of ITCA. EOM was applied on filter paper placed in Petri dishes (5.0 cm diameter). The dishes were covered with organza and placed inside glass jars of 0.8 L, and 50 adult insects were transferred to the jars, which were kept closed for 48 hours. EOM was used at concentrations ranging from 1.2 to 2.8 μL L-1. The S. zeamais populations used were from Abre Campo, Machado, Paracatu, Piracicaba and Tunápolis. The toxicity of EOM was evaluated by determining the lethal concentrations (CL) to 50 (LC50) and 95% (LC95) of adult insects, which were then used to estimate the toxicity ratio. The following locomotory behavioral parameters were studied: walked distance, walking velocity, resting time, and number of stops, as well as the number of takeoffs and flying height of the insects. Additionally, the instantaneous rates of increase (ri), the respiration rate (CO2 production) and body mass were evaluated for all populations. The most susceptible population to EOM was Piracicaba for wich the lowest LC50 was obtained (1.49μL L-1). This concentration was used for all the other assays treated with EOM, except the instantaneous rate of population growth, which hand no EOM treatment. The Paracatu population showed the highest LC50 (2.97 μL L-1) and LC95 (6.82 μL L-1) while Machado showed the lowest LC95 (2.16 μL L-1). The toxicity ratio based on the LC50 ranged from 1.08 to 1.99 times, and from 0.76 and 2.42 times based on the LC95. The slopes of the concentration mortality curves varied among the populations from 4.56 ± 0.72 (Paracatu) to 13.14 ± 0.75 (Tunápolis). The distance walked did not significantly differ between insects treatead with EOM and control or among populations. However, regarless of the population, the resting time of the insects was reduced by treatment with EOM. The other walking parameters (walking velocity and number of stops), flight parameters (flying height and number of takeoffs), respiratory rate, and body mass, the only varied among the populations, but no difference existed for insects exposed or not exposed to EOM. In conclusion, the EOM was toxic to the five populations of S. zeamais and did not promote major changes in the locomotory behavior of the insects. Different locomotory behavioral patterns, respiratory rate, and body mass were observed in the S. zeamais populations, but with uniform response to mustard oil; these differences should be inherent to the genetic make up of the populations.