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Aedes aegypti is the main vector of yellow fever, chikungunya, Zika, and dengue worldwide and is managed by using chemical insecticides. Though effective, their indiscriminate use brings in associated problems on safety to non-target and the environment. This supports the use of plant-based essential oil (EO) formulations as they are safe to use with limited effect on non-target organisms. Quick volatility and degradation of EO are a hurdle in its use; the present study attempts to develop nanoemulsions (NE) of Trachyspermum ammi EO and its constituent thymol using Tween 80 as surfactant by ultrasonication method. The NE of EO had droplet size ranging from 65 ± 0.7 to 83 ± 0.09 nm and a poly dispersity index (PDI) value of 0.18 ± 0.003 to 0.20 ± 0.07 from 1 to 60 days of storage. The NE of thymol showed a droplet size ranging from 167 ± 1 to 230 ± 1 nm and PDI value of 0.30 ± 0.03 to 0.40 ± 0.008 from 1 to 60 days of storage. The droplet shape of both NEs appeared spherical under a transmission electron microscope (TEM). The larvicidal effect of NEs of EO and thymol was better than BEs (Bulk emulsion) of EO and thymol against Ae. aegypti. Among the NEs, thymol (LC 50 34.89 ppm) had better larvicidal action than EO (LC 50 46.73 ppm). Exposure to NEs of EO and thymol causes the shrinkage of the larval cuticle and inhibited the acetylcholinesterase (AChE) activity in Ae. aegypti. Our findings show the enhanced effect of NEs over BEs which facilitate its use as an alternative control measure for Ae. aegypti., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: The occurrence of Spodoptera frugiperda (J.E. Smith) in Asia was reported for the first time from Karnataka in 2018. This pest is widely distributed in India, causing significant damage to maize. Management of this recent invasive pest in maize-growing regions of India relies on chemical control. Resistance is the greatest obstacle to the successful use of chemical insecticides to control this pest. Indiscriminate use of chemical insecticides destroys beneficial natural enemies, therefore effective and sustainable alternative control strategies are needed. In this case, the use of biological control agents is the alternative option to mitigate this pest. Thus, this study aimed to select virulent entomopathogenic nematodes (EPNs) isolates based on the laboratory assay and further to test the efficacy of virulent isolates in the field conditions along with commonly used chemical insecticide emamectin benzoate against S. frugiperda., Results: Laboratory results revealed that both Heterorhabditis indica 1 NBAIIH38 and Steinernema carpocapsae NBAIRS59 caused 100% mortality in third- and fourth-instar larvae of S. frugiperda, while these two species caused 85% and 72% mortality in pupae, respectively. When pupae of S. frugiperda were exposed to EPNs, pupae died after metamorphosis to malformed adults. All the nematode species were able to penetrate and reproduce within S. frugiperda larvae, but the reproduction rate for Heterorhabditids was higher than that of Steinernematids. Field trial results showed that H. indica 1 NBAIIH38 significantly reduced the number of larvae and leaf damage scores compared to S. carpocapsae NBAIRS59. Emamectin benzoate was more effective in reducing the larval population compared to EPN species. The cob yield was significantly higher in EPN- and emamectin benzoate-treated plots than in untreated control plots., Conclusion: Overall, these experiments suggest H. indica 1 NBAIIH38 is a promising biocontrol agent against S. frugiperda in maize production. © 2022 Society of Chemical Industry., (© 2022 Society of Chemical Industry.)

Housefly, Musca domestica L. is a pest of public health importance and is responsible for spreading diseases like typhoid, diarrhoea, plague etc. Indiscriminate reliance on synthetic insecticides has led to development of insecticide resistance and ill effect to humans and nontarget animals. This demands an alternative and safer pest control option. This study evaluates the biological effect of Piper betle L essential oil and its constituent eugenol, eugenol acetate, and β - caryophyllene on the housefly. The major components present in P. betel EO were safrole (44.25%), eugenol (5.16%), β -caryophyllene (5.98%), β -selinene (5.93%), α-selinene (5.27%) and eugenol acetate (9.77%). Eugenol caused 4.5fold higher ovicidal activity (EC 50 86.99 μg/ml) than P. betle EO (EC 50 390.37 μg/ml). Eugenol caused fumigant toxicity to adults (LC 50 88.38 mg/dm 3 ). On contact toxicity by topical application, eugenol acetate, eugenol and β-caryophyllene caused higher mortality to larval and adult stages than EO. FESEM (Field Emission Scanning Electron Microscope) images reveal that exposure to P. betle EO causes the shrinkage of the larval cuticle. Both EO and eugenol induced the detoxifying enzymes Carboxyl esterase (Car E) and Glutathione S - transferases (GST) in larvae and adults. EO and eugenol at 0.2% caused effective repellence and oviposition deterrence to M. domestica adults and this merits their use as alternative strategy to manage M. domestica., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Cotton leafhopper, Amrasca biguttula biguttula (Ishida) (Hemiptera: Cicadellidae) is a major sucking insect pest of cotton in India. Indiscriminate use of pesticides has led to the development of resistance to most of the recommended pesticide groups. Though there are multiple mechanisms and principles of insecticide resistance development in insects, the gut bacterial-mediated degradation of insecticides is relatively less explored. In the present study, the gut bacteria of field-collected, insecticide-resistant population of A. biguttula biguttula were compared with a laboratory-reared susceptible population. Among the five culturable gut bacteria from the imidacloprid-resistant population, only Enterococcus silesiacus CLHG1a exhibited growth in the agar medium amended with 50 and 100 ppm of imidacloprid. The imidacloprid degrading capacity of E. silesiacus CLHG1a was further confirmed by HPLC analysis. E. silesiacus and Bacillus amyloliquefaciens CLHG2 showed higher esterolytic activity (0.348 and 0.309 µmoles/min/mg respectively). The esterase zymogram on native PAGE revealed a single major band. This study provides clear evidence that the bacterium E. silesiacus isolated from the gut of A. biguttula biguttula has the ability to degrade imidacloprid and may have played a role in the detoxification of pesticides. [ABSTRACT FROM AUTHOR]