Background: The synanthropic housefly, Musca domestica, augments the transmission of several detrimental diseases like cholera and avian flu. Consequently, during the last century, many physico-chemical methods including synthetic compounds have been applied for its control. But these methods have proven to be prohibitive due to their side effects and serious issues like resistance development, environmental contamination, and detrimental effects on non-target fauna. Therefore, in view of these objectives, we investigated the effects of bay essential oil (EO) against M. domestica. Methods: The attractant/repellent assays were conducted by double choice technique. Different enzyme assays evaluating the effect of LC 50 concentration of the tested essential oil on larval gut were taken into consideration. To determine the composition, the tested oil was subjected to GC-MS/MS analysis. Further, the morphological alterations caused by EO treatment to third instar larvae were observed in a Nova Nano SEM machine. Data was statistically analyzed by one-way ANOVA using Tukey's test (p < 0.001). The LC 50 and LC 90 values were calculated by probit analysis. Results: The adulticidal bioassay revealed significant effects with LC 50 concentration as 43.03 mg/dm 3 against the newly emerged adult flies while in larvicidal assay mortality was dose dependent showing maximum effect at LC 50 0.0629 μg/cm 2. The pupicidal activity was more effective at a dose of LD 50 64.09 μl/0.25 L of air which either killed the pupae or caused deformity in the emerged adults. Likewise total sugar, protein, glycogen, and lipid contents of larvae were reduced after treatment with EO when compared with the normal larvae along with some gut enzymes. The EO reduced the acetylcholinesterase activity from 0.013 U/mg protein in normal larvae to 0.0093 U/mg protein after EO treatment. The GC-MS/MS analysis of the bay EO showed the abundance of myrcene, linalool, eugenol, chavicol, and anethole along with diterpenoid, geranylgeraniol. However, the insecticidal activity of tested EO might be majorly imparted by eugenol content. The FESEM analysis showed shrinkage of integument and distortion to intersegmental regions caused by the tested compound. Conclusion: The present study concludes the significant efficacy of bay EO against M. domestica which could be employed to breakdown its population below threshold levels to prevent the menace of vector-borne diseases.

The management of house fly, Musca domestica has become immensely important to prevent epidemics of many detrimental diseases. In view of this objective, the present study demonstrates the efficacy of lemongrass (LG) and tea tree essential oils (TTEOs) against M. domestica . The TTEO proved to be more lethal against larvae and adults of M. domestica depicting an LC 50 at 14.88 mg/ dm 3 which was 17.19 mg/ dm 3 for LGEO. In contrast, pupicidal effect of LGEO was much higher (LD 50 , 14.49 µl/0.25L) as compared to TTEO. The LGEO drastically reduced the total body sugar, glycogen and protein contents by 3.29, 2.95 and 7.56 fold, respectively, contrasting with high influence of TTEO on lipid content of the late 3rd instar larvae. A considerable reduction in gut enzymes secretion was observed due to treatment of EOs thereby altering gut physiology of the insect. Moreover, significant inhibition of acetylcholine esterase (AchE) was also observed with LGEO at LC 50 concentration (5.33 mg/ml) inhibiting insect neurotransmission. The gas chromatography-mass spectrometric (GC-MS) analysis of the LGEO showed 12 major compounds dominated by Citral whereas TTEO contained only 5 major compounds. Further analysis by field emission scanning electron microscopy (FESEM) revealed distortion and shrinkage of larval bodies caused by the treatment of EOs. These overall observations brand LG and TT-EOs as potential organic-insecticides against M. domestica . Graphic Abstract Supplementary Information The online version of this article (10.1007/s40011-020-01220-z) contains supplementary material, which is available to authorized users.

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The ever increasing energy demands of modern civilization and rapidly dwindling fossil fuels point towards a renewable substitute like biofuels. However, higher costs associated with biofuel productions is the major bottleneck for its commercialization. The present study demonstrates the use of a statistical approach called response surface methodology (RSM) to investigate the optimum parameters for maximum production of cellulase by Bacillus tequilensis G9. The Plackett-Burman design (PB) of the RSM analysis indicated grass straw (GS) concentration, pH, FeSO 4 , inoculum, MgSO4, incubation period and NH 4 Cl as significant variables that influence the cellulase production. Further, to propose the best medium for the maximum production of cellulase by B. tequilensis G9, the most influential parameters, namely concentrations of GS as substrate, FeSO 4 , pH, inoculum size, etc. were fine-tuned by central composite design (CCD) involving four factors and five levels. The CCD analysis demonstrated 8% substrate concentration, 1.5% of inoculum along with 10 ppm FeSO 4 and a pH of 5.5 in media as optimum conditions for highest enzyme production. The field emission scanning electron microscopic analysis of the treated GS showed structural alterations depicting significant deconstruction caused by B. tequilensis G9. The yield of the partially purified cellulase proteins were found to be 21% revealing molecular mass between 30 and 97 kDa. The enhanced cellulase production by B. tequilensis G9 demonstrated in our study brands its applications in many industrial processes like biorefinery, biofuels, etc.

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