ABSTRACT
AbstractInsecticides from plants have been studied as an alternative in agricultural production and in vector control of human diseases. The use of botanical insecticides may cause mortality in different stages, slow growth, infertile adults and decrease in viability of insect eggs. This study aimed to analyze the insecticidal potential of ethanol extract of Baccharis dracunculifolia DC, on Spodoptera frugiperda Smith, 1797 (Noctuidae) and Aedes aegypti L., 1762 (Culicidae). The botanical material was collected and prepared on February 8th, 2011 on the Fazenda Escola Três Barras (20°33'37.44043" S - 54°32'10.3824" W), Campo Grande, MS. The ethanol extract was prepared from dried leaves obtained of adult plants in a vegetative state at the Chemistry Laboratory of Anhanguera University-Uniderp. The experiments of biological activities were conducted at the Entomology Laboratory of the Catholic University Don Bosco, in a controlled environment with an average temperature of 25 ºC and photoperiod 12 hr. Experiments with S. frugiperda were conducted from August to October 2014. The collection of A. aegypti eggs was made in January 2014 and the treatments were done from March 10th to 17th, 2014. In the development of S. frugiperda the extract caused effect on caterpillars subjected to treatment at one and 10 days. The larval stage proved to be longer at both ages and pupal weight reduced at 10 days, as well as increased mortality at one day, when incorporated concentration 0.2 % into diet. The variables studied were mortality, larval duration, pupal weight, number and viability of the eggs. The bioassay used A. aedes third instar, 25 larvae per concentration, at four replicates. Parameters analysed for sublethal doses were pupal and larval, mortality, length larval and young (larva + pupa) the ethanol extract at concentrations 0.5 mg.mL-1 and 0.25 mg.mL-1. The extract resulted in deleterious effect on the development of caterpillars undergoing treatment in larvae of one and 10 days of age, the larval stage stretching, lower pupal weight in caterpillars 10 days and higher mortality in the group with one day of life. It did not interfere with the viability of eggs. In the life cycle of A. aegypti, the extract of B. dracuncufolia at the studied concentrations caused delay in the development of larval and pupal stages, and inhibited the emergence of adults in 85 % and 70 %. In laboratory conditions it can be said that the ethanol extract of B. dracunculifolia has a potential insecticide effect for both species of insects.
ResumenLos insecticidas de plantas han sido estudiados como una alternativa en la producción agrícola y el control de vectores de enfermedades humanas. El uso de insecticidas botánicos puede causar mortalidad en diferentes etapas, crecimiento lento, adultos infértiles y disminución en la viabilidad de huevos de insectos. Este estudio tuvo como objetivo analizar el potencial insecticida del extracto de etanol de Baccharis dracunculifolia DC, Spodoptera frugiperda Smith, 1797 (Noctuidae) y Aedes aegypti L., 1762 (Culicidae). Se recogió el material botánico y preparó el 8 de febrero 2011 en la Hacienda Escola Tres Barras. (20°33'37.44043" S - 54°32'10.3824" W), Campo Grande, MS. El extracto de etanol se preparó a partir de hojas secas obtenidas de plantas adultas en estado vegetativo en el Laboratorio de Química de la Universidad Anhanguera -Uniderp.Los experimentos de actividades biológicas se llevaron a cabo en el Laboratorio de Entomología de la Universidad Católica Don Bosco, en un ambiente controlado con una temperatura media de 25 °C y fotoperiodo de 12 hr. Los experimentos con S. frugiperda se llevaron a cabo de agosto a octubre 2014. La colección de huevos de A. aegypti se hizo en enero 2014 y los tratamientos se realizaron del 10 al 17 marzo 2014. En el desarrollo de S. frugiperda el extracto causa efecto sobre orugas sometidas a tratamiento de uno y 10 días. La etapa larval resultó ser más larga en ambas edades y el peso de la pupa se redujo a los 10 días; también, hubo aumento de la mortalidad en larvas de un día, cuando se incorporó la concentración 0.2 % en la dieta. Las variables estudiadas fueron la mortalidad, la duración de las larvas, el peso de las pupas, y el número y viabilidad de los huevos. El bioensayo utilizó A. aedes en tercer instar, y 25 larvas por concentración, en cuatro repeticiones. Los parámetros analizados para las dosis sub-letal fueran las pupa y larva, mortalidad, duración de las larvas y jóvenes (+ larva pupa) en el extracto de etanol a concentraciones de 0.5 mg.mL-1 y 0.25 mg.mL-1. El extracto resultó en efecto perjudicial sobre el desarrollo de las orugas de uno y 10 días de edad, sometidas a los tratamientos, prolongación de la fase larvaria, menor peso de pupa en las orugas de 10 días y una mayor mortalidad en el grupo con un día de vida. No hubo interferencia con la viabilidad de los huevos. En el ciclo de vida de A. aegypti, el extracto de B. dracuncufolia en las concentraciones del estudio, causó retraso en el desarrollo de las etapas de larva y pupa, y se inhibió la emergencia de los adultos en un 85 % y el 70 %. En condiciones de laboratorio, se puede decir que el extracto de etanol de B. dracunculifolia tiene potencial insecticida para ambas especies de insectos.
ABSTRACT
The fall armyworm, Spodoptera frugiperda, is one of the major field pests for maize production. It is mainly controlled by means of synthetic, and more recently by resistant cultivar of maize expressing Bt toxins. The neem tree, Azadirachta indica, is a plant that can potentially control insects with the advantage of being food and environmental safe. The aim of this study was to assess the effect of neem oil on the development and survival of S. frugiperda caterpillars by assessing histological alterations caused on their midgut. Newly hatched caterpillars were submitted to three neem oil concentrations: 0.006; 0.05; 0.4 percent, which were added to their artificial diet. Ten 3rd instar caterpillars, taken from each treatment, were submitted to histological analysis. The alimentary canals from the specimens were fixed in Baker for 12 hours, desiccated and diaphanized in alcohol/xylol (1:1) and xylol. After placing the samples in paraffin, they were sliced in 8 µm sections and stained with hematoxylin-eosin stain. The neem oil added to the diet of S. frugiperda caused total mortality at dose of 0.4 percent whilst still in the first instars, prolonged the larval and pupal stages, and reduced the pupal weight. Histo-physiological alterations such as degeneration of the epithelial lining of the midgut and in the peritrophic matrix were found at all concentrations of neem oil.
A lagarta-do-cartucho, Spodoptera frugiperda, é a mais importante praga da cultura do milho. Esta é usualmente, controlada por inseticidas sintéticos e mais atualmente por meio de variedades resistentes de milho com a toxina Bt. O nim Azadirachta indica é planta com potencial no controle de insetos, que possui as vantagens de segurança alimentar e ambiental. Objetivou-se com este estudo avaliar o efeito do óleo do nim no desenvolvimento e sobrevivência de lagartas de S. frugiperda em decorrência das alterações no mesêntero. As lagartas recém nascidas foram submetidas a três concentrações do óleo de nim: 0,006; 0,05; 0,4 por cento, adicionadas à dieta artificial. Dez lagartas do 3º instar, retiradas de cada tratamento, foram submetidas à análise histológica. O canal alimentar dos indivíduos foi fixado em Baker por 12 horas, desidratado, diafanizado em álcool/xilol (1:1) e xilol. Após a inclusão em parafina, as amostras foram seccionadas em 8 µm e coradas pela técnica de hematoxilina-eosina. Observou-se que o óleo de A. indica adicionado à dieta de S. frugiperda causa: mortalidade total na dosagem 0,4 por cento nos primeiros instares, aumento na duração do período larval e pupal, redução no peso de pupas. Alterações histofisiológicas, como degeneração do epitélio do revestimento do mesêntero, da matriz peritrófica foram registradas em todas as concentrações do óleo de neem.