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Pest management with natural botanical insecticides is a significant implementation for the sustainability of agroecosystem by reducing the unnecessary risk from the inputs of synthetic insecticides. In this research, we isolated the bioactive compound cucurbitacin E from Citrullus colocynthis (L.) Schrad, and their toxicological effects were screened against different larval instars of Spodoptera litura. The bioactive compound cucurbitacin E was chemically characterized through TLC, FT-IR, and NMR analyses. The larval mortality bioassay revealed that the larvae exposed to cucurbitacin E at the discriminating dose of 50 ppm display higher mortality rate against second (93.8%), third (86.4%), and fourth (73.2%) instar respectively. The lethal concentrations (LC 50 and LC 90 ) was detected as 15.84 and 67.60 ppm for third instar respectively. The sub-lethal concentration of cucurbitacin E (2, 4, and 6 ppm) intentionally altered the percentage of survival, pupation, fecundity, and egg hatchability of S. litura. Moreover, antifeedant activity of cucurbitacin E was analyzed using choice-based test. In addition, we found the toxic effects of cucurbitacin E (50 and 100 ppm) and chemical pesticides (cypermethrin and monocrotophos) against terrestrial beneficial earthworm Eisenia fetida, and the result revealed that cucurbitacin E has no harmful effect on non-target organism. Hence, the present study reveals that cucurbitacin E might be a part of a new biorational product alternative to synthetic pesticides.

Toxicological screening of Swietenia mahagoni Jacq. (Meliaceae, West Indies Mahogany) against the lepidopteran pest Spodoptera litura was examined. Phytochemical screening through GC-MS analysis revealed nine peaks with prominent peak area % in Bis (2-ethylhexyl) phthalate (31.5%) was observed. The larvae exposed to discriminating dosage of 100 ppm deliver significant mortality rate compare to other treatment concentrations. The lethal concentrations (LC 50 and LC 90 ) was observed at the dosage of 31.04 and 86.82 ppm respectively. Sub-lethal concentrations (30 ppm) showed higher larval and pupal durations. However, pupal weight and mean fecundity rate reduced significantly. Similarly, the adult longevity reduced significantly in dose dependent manner. Midgut histology studies showed that the methanolic extracts significantly disturbs the gut epithelial layer, lumen and brush border membrane compare to the control. The soil assay on a non-target beneficial organism, the soil indicator earthworm Eudrilus eugeniae, with extracts from S. mahagoni (200 mg/kg) showed no toxicity compared to Monocrotophos at the dosage of 10 ppm/kg. Current results suggest that this bio-rational plant product from S. mahagoni displays a significant effect to reduce lepidopteran pests with low toxicity to other beneficial species., (Copyright © 2018. Published by Elsevier Ltd.)

Comparative toxicity of two chemical pesticides (temephos and monocrotophos) versus a plant-derived betel leaf oil Piper betle (L.) to earthworm Eudrilus eugeniae (Kinberg) and redworm Eisenia fetida Savigny, historically: Eisenia foetida (Savigny 1826), was evaluated. Mortality rate was more prominent in temephos at 100 μg concentration to both the earthworms in filter paper test (FPT) as well as 10 mg concentration in artificial soil test (AST). In contrast, P. betle does not display much mortality rate to both the earthworms even at 1000 mg of treatment concentrations. The lethal concentration (LC 50 ) value was observed at 3.89 and 5.26 mg/kg for temephos and monocrotophos against E. eugeniae and 3.81 and 5.25 mg/kg to E. fetida, respectively. Whereas, LC 50 value of betel leaf oil was only observed at 3149 and 4081 mg/kg to E. eugeniae and E. fetida, respectively. Correspondingly, the avoidance or attraction assay also displayed that earthworms were more sensitive to the soil containing chemical pesticides. Whereas, the avoidance percentage was decreased in the P. betle oil. Similarly, sublethal concentration of chemical pesticides (5 and 6.5 mg) significantly reduced the earthworm weight and growth rate. However, P. betle oil did not change the developmental rate in the duration of the assay (2, 7 and 14 days) even at 4000 mg treatment concentration. The enzyme ratio of CAT and SOD was also affected significantly after exposure to the chemical pesticides (6.5 mg/kg). Hence, our study implied the risk assessment associated with the chemical pesticides and also recommends plant-derived harmless P. betle oil against beneficial species as an alternative pest control agent.

A novel flavonoid, quercetin, was isolated from the medicinal plant Euphorbia hirta L. through chromatography techniques including: TLC, Column chromatography, NMR and then screened for toxicity to larvae of Spodoptera litura Fab. Bioassays were used to analyze pupal weight, survival rate, fecundity, egg hatchability, population growth index, Nutritional index and histopathology of treated larvae at a range of E. hirta extract concentrations. Results of toxicity assays demonstrated that, 6 ppm of quercetin caused 94.6% mortality of second, 91.8% of third, 88% of fourth, and 85.2% of fifth instars respectively. The lethal concentrations (LC 50 and LC 90 ) was calculated as 10.88 and 69.91 ppm for fourth instar larvae. The changes in consumption ratio and approximate digestibility produced a reduction in growth rates. Histopathology examinations revealed that the cell organelles were severely infected. Analyses of earthworm toxicity effects resulted in significantly lower rates compared to synthetic insecticides (chloropyrifos and cypermethrin). These results suggests that the botanical compound (quercetin), could have a part as a new biorational product which provides an ecofriendly alternative. Validation of the potential of quercetin, still needs to be demonstrated under field conditions, where formulation will be important in maintaining the activity., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Botanical insecticides may provide alternatives to synthetic insecticides for controlling Spodoptera litura (F.) and they are target specific, biodegradable, and harmless to mammals. Eight natural chemical compounds with larvicidal activity were identified from fraction F6 of C. guianensis flower extract. Probit analysis of 95% confidence level exposed an LC50 of 223ppm against S. litura third instar larvae. The growth and development of S. litura was affected in sub-lethal concentrations of fraction F6 (50, 100, 150 and 200ppm) compared to controls. Similarly nutritional indices values decreased significantly compared to controls. Fraction F6 also damaged the gut epithelial layer and brush border membrane (BBM). This study also resolved the effects of toxicity to non-target earthworm treated with fraction F6 and chemical pesticides (monotrophos and cypermethrin) and the results showed that fraction F6 had no harmful effect on E. fetida. Further, fraction F6 was eluted and sub fractions F6c (50ppm) showed high mortality against S. litura third instar larvae. Octacosane from fraction F6c was established and confirmed using IR spectrum and HPLC. The time of retention of fraction F6c was confirmed with the octacosane standard. Fraction F6 of C. guianensis extract caused dose-dependent mortality towards S. litura. Octacosane in fraction F6c was establish to be the prominent chemical compound associated with causing mortality but other compounds present in the fraction F6 were shown to be associated with changes in development of S. litura at low dosages. S. litura at low dosage. Therefore, these findings suggest that octacosane may be one of the major insecticidal compounds affecting S. litura survival., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Evaluations of biological effects of (Pb-CVO) the crude volatile oil of Piper betle leaves on the tobacco cutworm Spodoptera litura were conducted. Pb-CVO was subjected to GC-MS analysis and twenty vital compounds were isolated from the betel leaf oil. Pb-CVO was tested at four different concentrations (0.25, 0.5, 1.0 and 1.5%) against S. litura. The treated insects exhibited dose depended mortality. The mortality rate was significantly higher at the 1.0 and 1.5% Pb-CVO. The LC50 (Lethal concentration) were observed at 0.48% Pb-CVO. Larval and pupal durations increased in all treatment concentrations (0.25, 0.3, 0.4 and 0.5%) whereas, pupal weight decreased compared to control. Adult longevity of S. litura was reduced in all treatments but predominantly in the 0.4 and 0.5% Pb-CVO. Correspondingly, mean fecundity rate was reduced at all concentrations compared to control. Histological studies of larvae mid-gut profiles of S. litura were severely damaged in 1.0 and 1.5% and showed abnormalities in mid-gut cells with 0.25 and 0.5% Pb-CVO treatments. Earthworm toxicity illustrated that 0.1% of chemical insecticides (monocrotophos and cypermethrin) varied widely in their contact toxicities compared to 0.5 and 1.0% Pb-CVO and control in both contact filter paper and artificial soil test. These findings suggest that twenty essential compounds of betel leaf oil were significant inhibitors of the development and caused behavioral changes of S. litura. Treatment with betel leaf oil at these concentrations had no adverse effect on earthworm populations., (Copyright © 2016 Elsevier Ltd. All rights reserved.)