Chemical composition and larvicidal activity of the essential oil of Pimenta dioica leaves

In this study, we investigated the main constituent, the predominant class and biological activity of the essential oil extracted from the leaves of Pimenta dioica and the pattern of the major constituent against larvae in the third stage of Aedes aegypti. For this reason, we extracted the oil by hydrodistillation, identified its components by gas chromatography coupled with mass spectrometry (GC/MS) and calculated the lethal concentration (LC50) of the larvicidal activity using the Reed-Muench method. The results show that the oil consists mainly of eugenol, in which the phenylpropanoid class predominated and the lethal concentration, LC50, was 38.86 μg mL-1at a confidence level of 2.25 μg mL-1, while the eugenol standard presented LC5079.75 μg mL-1at a confidence level of 2.10 μg mL-1. Given the facts, we conclude that the oil is more active than the standard and that it has the potential to replace chemical larvicides.

Susceptibility of Plutella xylostella (L.) to Bacillus thuringiensis Berliner strains

The objective was to observe the susceptibility of a population of Plutella xylostella (L.) maintained for 100 generations in laboratory to strains of Bacillus thuringiensis Berliner. The concentrations 9×104, 1.5×105, 6×105, 8×105, 9×105, 1.5×106, 2×106, 3×106, 4.5×106, 6×106, 7.5×106, 9×106, 1.5×107, 2×107, 3×107, 4×107, 4.5×107, 6×107, 7.5×107, 9.5×107, 1.5×108 e 3×108 spores/mL were evaluated for the strains: E1, 49.30A, E2, 1.7L, T3A.259, T3A.140, T08024, E26, E22 and T07. The strains E26, E22 and T07 did not cause mortality for P. xylostella larvae. The P. xylostella larvae have a very high susceptibility pattern to the concentrations evaluated for six strains tested (E1, 49.30A, E2, 1.7L, T3A.259 and T3A.140). Only the T08.024 strain allowed the estimation of lethal concentration that kills 50% of the population (2.7 spores/mL).

Potensi Ekstrak Jahe Merah (Zingiber Officinale Var. Rubrum) Sebagai Larvasida Alami Aedes Albopictus

DBD masih merupakan masalah kesehatan masyarakat utama di Indonesia. Upaya pencegahan yang dilakukan saat ini menggunakan insektisida berbahan dasar kimia yang dapat merusak lingkungan juga menimbulkan resistensi. Penggunaan larvasida alami dari tumbuhan dapat menjadi alternatif insektisida, salah satunya adalah jahe merah (Zingiber officinale var. rubrum) yang dapat dijadikan sebagai insektisida alami karena adanya kandungan senyawa aktif. Tujuan penelitian ini adalah untuk mengetahui tingkat kematian, perbedaan rerata kematian larva Aedes albopictus serta mengetahui Lethal Time dan Lethal Concentration. Jenis penelitian ini merupakan penelitian true eksperimental dengan posttest only control group design. Hasil penelitian menunjukkan bahwa kematian larva 100% lebih cepat pada konsenrasi 8% yaitu setelah 6 jam pengujian. Hasil Uji Kruskal Wallis untuk melihat perbedaan rerata kematian larva setiap jam kelompok perlakuan ekstrak jahe merah dengan kelompok kontrol menunjukkan terdapat perbedaan secara signifikan rerata kematian larva (0,000 < 0,05). Hasil uji probit Lethal Time menunjukkan bahwa diperlukan waktu 2,196 jam dalam mematikan 50% larva dan 4,788 jam dalam mematikan 99% larva dengan konsentrasi 8% sedangkan Lethal Concentration menunjukkan bahwa diperlukan konsentrasi sebesar sebesar 0,772% dalam mematikan 50% larva dan 1,973% dalam mematikan 99% larva setelah 9 jam pengukuran. Perlu dilakukan penelitian lebih lanjut untuk mengembangkan ekstrak jahe merah yang aman dan layak pakai namun tidak menghilangkan senyawa yang ada pada ekstrak jahe merah.

Determination of Median Lethal Concentration (LC50) for Endosulfan, Heptachlor and Dieldrin Pesticides to African Catfish, Clarias gariepinus and Their Impact on Its Behavioral Patterns and Histopathological Responses

Pesticides such as endosulfan, heptachlor and dieldrin persist in aquatic environments as a result of their resistance to biodegradation. However, there is no adequate information about the toxicity of endosulfan, heptachlor and dieldrin to the aquatic organism, African catfish (Clarias gariepinus)—a high valued widely distributed commercially interesting species. The current experiment was performed with the aim to determine the median lethal concentration (LC50) of endosulfan, heptachlor and dieldrin to African catfish (Clarias gariepinus); their behavioral abnormalities and histopathological alterations in several vital organs. A total of 324 juvenile fish were exposed for 96 h to six concentrations of endosulfan and dieldrin at 0, 0.001, 0.002, 0.004, 0.008 and 0.016 ppm, and to heptachlor at concentrations of 0, 0.02, 0.04, 0.08, 0.16 and 0.32 ppm for dose-response tests. The study demonstrated that the species is highly susceptible to those contaminants showing a number of behavioral abnormalities and histopathological changes in gill, liver and muscle. The 96-h LC50 value of endosulfan, dieldrin and heptachlor for the African catfish was found as 0.004 (0.001−0.01) mg/L, 0.006 mg/L and 0.056 (0.006−0.144) mg/L, respectively. Abnormal behaviors such as erratic jerky swimming, frequent surfacing movement with gulping of air, secretion of mucus on the body and gills were observed in response to the increasing exposure concentrations. Histopathological alterations of liver, gill and muscle tissues were demonstrated as vacuolization in hepatocytes, congestion of red blood cells (RBCs) in hepatic portal vein; deformed secondary lamellae and disintegrated myotomes with disintegrated epidermis, respectively. These findings are important to monitor and responsibly manage pesticide use in and around C. gariepinus aquacultural areas.

Toxic Effect of Monocrotophos on Various Blood Parameters in Edible Freshwater Fish Oreochromis Mossambicus (Tilapia)

In modern agriculture, farmers are using the authenticity of pesticides for agricultural activities. Water bodies are often polluted with various harmfull chemical substances. Fishes are very important for human nourishment. In this study, the effect of Pesticide monocrotophos on various hematological parameters such as RBC, WBC, and Hemoglobin was observed in freshwater fish Oreochromis mossambicus. The fish were exposed to various sub-lethal concentrations (1/10, 1/20, and 1/30) of Monocrotophos for 10, 20, and 30 days. The blood samples were analyzed at the end of every exposure period. Increased count of WBC observed in Lower Sub lethal concentration (21.25, 21.76, 22.01), Medium Sub-lethal concentration (21.69, 22.48, 22.89), and Higher Sub lethal concentration (22.47, 23.54, 23.69) of monocrotophos at various monocrotophos exposure periods on experimental fish Oreochromis mossambicus. Decreased count of RBC observed in Lower Sub-lethal concentration (3.58,3.21,3.08), Medium Sub-lethal concentration (2.97,2.35,2.19) and Higher Sub-lethal concentration (2.41,2.16,2.02) and decreased level of Hemoglobin were observed in Lower Sub-lethal concentration (21.25,21.76,22.01), Medium Sub-lethal concentration (21.69,22.48,22.89) and Higher Sub-lethal concentration (22.47,23.54,23.69) of monocrotophos at various exposure period on fish Oreochromis mossambicus. The 1/10 sub-lethal concentration of monocrotophos showed a high level of variation on 30th-day exposure. Reduction of RBC indicates hemolysis in fish and increased WBC count has been considered to be an adaptation of animals to meet stressful conditions. In the present study, it was found that the effect of monocrotophos alters the activity of various blood parameters in freshwater fish Oreochromis mossambicus. Therefore, the experiment is an attempt to study the toxicity of the pesticide Monocrotophos concerning blood parameters of freshwater fish Oreochromis mossambicus. It is concluded from this study that exposure to Monocrotophos affects the hematological parameters of fish.

Efficacy of Beauveria bassiana against the cotton leaf roller, Haritalodes (Syllepte) derogata (Fabricius, 1775) (Lepidoptera: Crambidae) under laboratory conditions.

Objective: The leaf-roller caterpillar Haritalodes (=Syllepte) derogata (Fabricius, 1775) (Lepidoptera: Crambidae) induces high yield losses by damaging cotton leaves and reducing the photosynthetic activity of the plant. Laboratory bioassays were carried to evaluate the effect of Beauveria bassiana on the survival of H. derogata larvae. Methodology and results: In the first trial, screening of thirteen B. bassiana isolates was performed on third larval instars at 107 conidia.mL-1 . In the second trial, effects of five concentrations (105 to 109 conidia.mL-1 ) of the three best isolates of the fungus were tested. Conidia suspension was applied on each larva topically. Germination rates of conidia used varied between 90.2% to 95.7%, 24 hours after incubation. Five isolates were found to be the most promising namely Bb116, Bb3, Bb11, Bb6 and Bb115. In the second bioassay, caterpillar mortality increased with fungal concentration. Lethal Concentration (LC50) was estimated to 1.18x1015 conidia.mL-1 , 1.75x1013 conidia.mL-1 , 1.75x1013 conidia.mL-1 , 9 days after inoculation for Bb3, Bb11 and Bb115, respectively. Conclusion and application of results: The use of B. bassiana as a biopesticide against H. derogata could be a good alternative method to control the pest. It is an environmentally friendly method with less side effects compared to the application of synthetic pesticides on cotton. This method could be tested in future station and field experiments. Keywords: Cotton, Integrated pest management, Haritalodes (=Syllepte) derogata, Beauveria bassiana, Lethal Concentration.

Ultrastructural Changes of the Digestive Tract of Pomacea canaliculata Exposed to Copper at Lethal Concentration

The present study was undertaken to elucidate the basis of cellular reactions and to verify the suitability of Pomacea canaliculata digestive tract ultrastructure as a biomarker for assessing the Cu pollution in freshwater environments. Two-month-old P. canaliculata were exposed to 96-h lethal concentration of Cu (0.15 mg L-1) for 96 h. Electron microscope investigations showed different alterations of organelles in the epithelial cells lining the esophagus and intestine. The most striking changes were damages to the mitochondria, RER, and nucleus typified by loss of cristae and degeneration of mitochondria; degranulation and fragmentation of RER. In nucleus, karyolysis and rupture of nuclear envelope were observed. These changes were attributed to membrane destabilization and increased membrane permeability to ions under the influence of toxicants or heavy metals. These findings indicate the possibility of using the P. canaliculata as biomonitor for Cu contamination in the freshwater environment.

Effects of Chlorpyrifos Ethyl on Cholinesterase and Growth of Silver Barb (Barbonymus gonionotus)

Chlorpyrifos ethyl is a popular insecticide widely used in agriculture within the Vietnamese Mekong delta, including for rice farming. Here, local farmers often apply pesticides at very high rates which leads to contamination of the surrounding environment. Silver barb (Barbonymus gonionotus) is a fish species indigenous to the delta, which resides in a variety of water bodies and is also commonly cultivated in rice–fish systems. As a result, this species is at high risk of exposure to chlorpyrifos ethyl. This study aims to determine the lethal concentration (LC50) of chlorpyrifos ethyl, as well as the effects of sub-lethal concentrations on the activity of cholinesterase and growth of Silver barb. Lethal concentration testing was conducted in a static non-renewed system. Three concentrations of chlorpyrifos ethyl (1%, 10% and 20% LC50-96 h) were conducted in triplicate to assess the effects of chlorpyrifos ethyl on the brain cholinesterase (ChE) of fingerling fish for 15 days, and on their growth for 60 days. Results showed that chlorpyrifos ethyl was highly toxic to fingerling Silver barb with a LC50-96 h of 0.119 ppm. The lowest observed effect concentration (LOEC) was 1%LC50-96 h for ChE and 10%LC50-96 h for growth. No observed effect concentration (NOEC) of chlorpyrifos ethyl for growth was 1%LC50-96 h. The result from this study suggests that ChE activity is significantly inhibited at environmentally realistic concentrations in the Vietnamese Mekong delta and can be used as a biomarker of pesticide exposure. Further study in the rice fields as well as in the canals or rivers is required.

The Transcriptomic Landscape of Molecular Effects after Sublethal Exposure to Dinotefuran on Apis mellifera

The decreasing number of bees is a global ecological problem. With the advancement of agricultural modernisation, the large-scale use of neonicotinoid insecticides is one of the main factors leading to the decline of bees. The aim of the present study was to investigate the effect and the mechanisms underlying bees impaired by dinotefuran. Acute (48 h) oral toxicity tests showed that a 5% lethal concentration (LC5) was 0.220 mg/L, and a 20% lethal concentration (LC20) was 0.458 mg/L. The gene expression profile shows that when compared with the control group, the LC5 group induced 206 significantly upregulated, differentially expressed genes (DEGs) and 363 significantly downregulated DEGs, while the LC20 group induced 180 significantly upregulated DEGs and 419 significantly downregulated DEGs. Significantly, transcriptomic analysis revealed DEGs involved in immunity, detoxification, and the nervous system, such as antimicrobial peptides, vitellogenin, synaptotagmin-10, AChE-2, and nAChRa9. Furthermore, Gene Ontology (GO) annotation and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway analysis revealed that DEGs were enriched in amino acid and fatty acid biosynthesis and metabolism pathways. Collectively, our findings will help clarify the deleterious physiological and behavioural impacts of dinotefuran on bees and provide a basis for future research on the mechanisms underlying bees impaired by dinotefuran.