Essential oil of Cinnamodendron dinisii Schwanke for the control of Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) / Óleo essencial de Cinnamodendron dinisii Schwanke para controle de Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

ABSTRACT The use of natural compounds is a less aggressive alternative for the control of insects in stored grains, in relation to synthetic chemical agents. Plants with insecticidal properties can be used as a source of these compounds to the direct application in pest control. In this work, the essential oil of Cinnamodendron dinisii was chemically characterized and tested regarding its insecticidal and repellent effect on the control of Sitophilus zeamais in stored grains. The essential oil was obtained by hydrodistillation and analyzed by gas chromatography–mass spectrometry (GC-MS). The insecticidal potential was evaluated through the maintenance of the insects during 24 hours in contact with several doses of the oil, in the absence of feed substrate. The Bioassays of repellency were conducted with lethal doses (LD5, LD25, LD50 and LD95) obtained from insecticidal bioassay. In order to compare the treatments, the preference index (PI) was used. The essential oil of C. dinisii had insecticidal activity against S. zeamais, causing a linear and crescent mortality with LD of 0.04, 0.17, 0.34 and 0.63 µL/cm2, respectively. The repellency ranged from 55.4% to 85.2%, using the LD values previously mentioned. The DL5 was neutral regarding repellence (PI index -0,09), but from DL25 on, the PI index was between -0.1 and -1.0, indicating repellence activity.

RESUMO O uso de compostos naturais é uma alternativa menos agressiva para o controle de insetos em grãos armazenados em relação aos agentes químicos sintéticos. Plantas com propriedades inseticidas podem ser usadas como fonte destes compostos para a aplicação direta no controle de pragas. No presente trabalho, o óleo essencial de Cinnamodendron dinisii foi caracterizado quimicamente e testado em relação ao seu efeito repelente inseticida no controle de Sitophilus zeamais em grãos armazenados. O óleo essencial foi obtido por hidrodestilação e analisado por cromatografia gasosa-espectrometria de massa (GC-MS). O potencial inseticida foi avaliado pela manutenção dos insetos durante 24 horas em contato com várias doses de óleo, na ausência de substrato alimentar. Os bioensaios de repelência foram realizados com as doses letais (DL5, DL25, DL50 e DL95) obtidas do bioensaio inseticida. Para comparar os tratamentos foi utilizado o índice de preferência (PI). O óleo essencial de C. dinisii apresentou atividade inseticida sobre S. zeamais, causando mortalidade linear e crescente com DL de 0,04, 0,17, 0,34 e 0,63 µL/cm2, respectivamente. A repelência variou entre 55,4% até 85,2%, utilizando os valores de DL acima mencionados. A DL5mostrou-se neutra em relação à repelência (índice PI -0,09), mas a partir de DL25 o índice PI foi entre -0,1 e -1,0, indicando atividade de repelência.

Evaluation of the role of ATP-binding cassette transporters as a defence mechanism against temephos in populations of Aedes aegypti

The role of ATP-binding cassette (ABC) transporters in the efflux of the insecticide, temephos, was assessed in the larvae of Aedes aegypti. Bioassays were conducted using mosquito populations that were either susceptible or resistant to temephos by exposure to insecticide alone or in combination with sublethal doses of the ABC transporter inhibitor, verapamil (30, 35 and 40 μM). The best result in the series was obtained with the addition of verapamil (40 μM), which led to a 2x increase in the toxicity of temephos, suggesting that ABC transporters may be partially involved in conferring resistance to the populations evaluated.

A study of neurotoxicity of BHC in relation to residual accumulation on the brain tissue of Heteropneustes fossilis (Bloch).

Neurotoxic effect of BHC, the organochlorine pesticide in Heteropneustes fossilis has been studied exposing at the dose concentrations of 1 ppm, 5 ppm and 10 ppm in lab aquarium for 96 hours over a period of one year. The results showed the behavioural abnormalities in different exposure concentrations such as dysfunction of endocrine gland, excretion of mucus, dispigmentation, sign of restlessness, erratic swimming with rapid jurkey movement, spiralling and convolution showing severe effect in central nervous system. Therefore an attempt has been made for monitoring of BHC residues viz. alpha, beta, gamma isomers in the brain tissue exposed to different sublethal concentrations using Gas liquid chromatography. The mean values of isomers were found to be 1.587 microg/gm for 1 ppm, 2.993 microg/gm for 5 ppm and 3.78 microg/gm for 10 ppm test group. Severe behavioural abnormalities were recorded at high dose concentration of pesticides with higher accumulation of pesticide residues in brain tissue.

Toxicity and residue studies of fenvalerate to some selected freshwater fishes.

The toxicity test of fenvalerate were conducted to fresh water fishes Labeo rohita (Hamilton), Catla catla (Hamilton), Cirrhinus mrigala (Hamilton), Aplocheilus punchex (Hamilton) and Ctenopharygodon idellus (Valenciennes). The static and continuous flow through tests were employed to determine the lethal concentration (LC50) for 24h, 48h and 96h to the test fish. It was observed that Cirrhinus mrigala is more sensitive to this pesticide followed by Applochielus punchex, Lebeo rohita, Catla catla and Ctenopharyngodon idellus. The residue analysis for qualitative confirmation was done by thin layer chromatography (TLC) to assess the deposition of pesticide in different tissues of fishes. The quantitative study of accumulation in the whole body tissue was done by Gas liquid chromatography (GLC). The quantitative residues confirm the toxic action.

Effect of short-term dermal toxicity of fenvalerate on residue, cell architecture and biochemical profiles in broiler chicks.

Effect of fenvalerate on cell architecture, tissue biochemical parameters and its residual concentration was studied in broiler chicks following dermal application at 0.1 and 1% in ethanol once daily for 31 days. It did neither produce loss of body weight nor clinical signs of toxicity. Kidney contained maximal residue followed by heart, fat, liver and brain after 0.1%; and fat contained maximal residue followed by kidney, heart, liver and brain after 1% application. Fenvalerate (0.1%) increased the aspartate aminotransferase (AST) (except brain), alanine aminotransferase (ALT), alkaline phosphatase (AP), acid phosphatase (AcP) (only brain) activities, glycogen level (only liver) in liver, kidney, heart and brain tissues; and 1% increased the AST (except brain), ALT, AcP (except liver and kidney), AP (only heart), glycogen (only liver) and decreased AP (except heart), AcP (only kidney), cholesterol (except liver and heart), and acetylcholinesterase (AChE) (liver and brain) of liver, kidney, heart and brain tissue homogenates respectively. Histopathological examination in general showed aggregation of mononuclear cells in liver, around the kidney tubules and cardiac muscle fibre. In addition, fibrosis in the periportal area of liver, proliferation of ureter and tubular degeneration, and congestion of endocardial vessels were also observed. The intensity of cellular changes was more marked after 1% dermal application.