Insecticidal and repellent activity of native and exotic lemongrass on Maize weevil.

Corn crop, due to its easy adaptation to the most diverse agroecosystems, spreads throughout the different regions of the world, making it one of the most important agricultural crops. In this crop, pest insects stand out for causing losses both in the field and in warehouses. The application of essential oils can be an important technique to be investigated in the management of insects due to its known insecticidal activity and low risk to the environment. The objective of the work was to value the insecticide and repellent effect of essential oils of exotic lemongrass (Cymbopogon citratus) and native lemongrass (Elionurus sp.) for the management of maize weevil (Sitophilus zeamais (Mots., 1855, Coleoptera: Curculionidae)). The chemical analysis of the oils made by CG-MS showed that the chemical composition of the native and exotic lemongrass is similar, however, the exotic species presented a greater number of compounds. The essential oils of native and exotic lemon grass have efficiency on maize weevil mortality, and it is verified that the increase in the applied dose reflects in a reduction in the insect's exposure time for death to occur. The essential oil of both species showed repellent capacity at all times evaluated. Thus, it can be said that both species have the capacity and potential to be used in the management of corn weevil, and can be an alternative for smallhorders farmers and organic production.

Avaliação das curvas de secagem de guaco (Mikania glomerata Spreng. ) em secador de bandejas / Evaluation of drying curves of Mikania glomerata Spreng. in a tray dryer

Esse trabalho teve como objetivo avaliar diferentes modelos matemáticos para determinar a curva de secagem de guaco. Para a condução do experimento, foi utilizado um secador com ventilação forçada, com 4 bandejas, empregando gás liquefeito de petróleo como fonte de aquecimento. Foram realizados 6 tratamentos de secagem: com ar aquecido a 40, 50, 60, 70 e 80ºC, e com ar a temperatura ambiente. Para todos os tratamentos a velocidade do ar de secagem passando através da massa de plantas foi mantida em, aproximadamente, 0,5 m s-1. Para ajuste dos modelos matemáticos aos dados experimentais realizou-se análise de regressão não-linear pelo método Quasi-Newton empregando-se o programa computacional STATISTICA 6.0®, sendo os valores dos parâmetros dos modelos estimados em função da temperatura do ar de secagem. Apenas o modelo proposto por Midilli et al. apresentou ajuste satisfatório para descrever o processo de secagem de guaco, independentemente da temperatura do ar de secagem, enquanto o modelo da aproximação da difusão se adequou para a temperatura ambiente e com ar aquecido a 60ºC.

This work aimed to evaluate different mathematical models to determine the curve of the drying of Mikania glomerata Spreng. . For the conduction of the experiment, a drier with forced ventilation was used, with 4 trays, using liquefied petroleum gas as heating source. Six drying treatments were carried out, that is, with hot air at 40, 50, 60, 70 and 80ºC, as well as drying with air at room temperature. For all the treatments, the drying air speed, through the mass of plants, were kept at, approximately, 0.5 m s-1. For the adjustment of the mathematical models to the experimental data, nonlinear regression analysis was performed through the Quasi-Newton method, using the computational program STATISTICA 6.0®, and the values of the parameters of the models were estimated in function of the temperature of the drying air. But only the model considered by Midilli et al. presented satisfactory adjustment to describe the process of drying Mikania glomerata Spreng., regardless of the temperature of the drying air, while the model of diffusion approximation was suitable for room temperature and hot air at 60ºC.

Rendimento extrativo de cumarina de folhas de guaco (Mikania glomerata Sprengel) submetidas a diferentes temperaturas de secagem / Extraction yield of coumarin from guaco (Mikania glomerata Sprengel) leaves subjected to different drying temperatures

O objetivo deste trabalho foi avaliar o efeito da temperatura do ar de secagem no rendimento extrativo da cumarina de folhas de guaco. Foram empregados 6 tratamentos de secagem, sendo ar ambiente, ar aquecido a 40, 50, 60, 70 e 80ºC. Utilizou-se secador de bandejas, tendo como fonte de aquecimento o gás liquefeito de petróleo (GLP). Os rendimentos extrativos da cumarina, depois de realizada a secagem, foram comparados com os valores obtidos da planta fresca (tratamento testemunha). A extração da cumarina foi realizada pelo método a quente, em banho-maria a 65ºC, sendo a identificação e quantificação realizada por cromatografia líquida de alta eficiência (CLAE). Em função dos resultados obtidos, pôde-se concluir que a temperatura do ar de secagem a 50ºC possibilitou o melhor resultado para o rendimento extrativo de cumarina em folhas de guaco.

The aim of this study was to evaluate the effect of drying on the extraction yield of coumarin from guaco leaves. Six drying treatments were used, being room air, heated air at 40, 50, 60, 70 and 80ºC. A tray dryer was used with liquefied petroleum gas (LPG) as heating source. The extraction yield of coumarin, after drying, was compared to the values obtained from the fresh plant (control treatment). Coumarin extraction was carried out by using the heat method, in water bath at 65ºC, and identification and quantification were done by means of high performance liquid chromatography (HPLC). Considering the obtained results, the temperature of the drying air at 50ºC led to the best result for the extraction yield of coumarin in guaco leaves.