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Subject: Agricultural Entomology × Author: Begum, Asma × Start date: 2018 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Biosynthesis and utilization of plant based silver nanoparticles (AgNPs) against red spider mite, Oligonychus coffeae
    (2023) Begum, Asma; Kalita, Surajit
    The present investigation on biosynthesis of silver-nanoparticles synthesized from Phlogocanthus thyrsiflorus leaf extract was carried out at Department of Plant Pathology, Assam Agricultural University (AAU), Jorhat and their bioefficacy against Oligonychus coffeae was carried out at Department of Entomology, AAU, Jorhat during 2021-2023. Characterization of the biosynthesized AgNPs through UV-Vis spectrophotometer in wavelength range of 250-600 nm revealed a peak at 417 nm, which confirmed the formation of silver nanoparticles. Dynamic Light Scattering (DLS) analysis (Z-average of 45.31 nm and polydispersity Index, PDI of 0.286) and Zeta potential (Charge: -22.5 mV) analysis were conducted to characterize the dispersion pattern of the nanoparticles. The size of the AgNPs was calculated to be around 5 nm through TEM analysis with relatively uniform circular and spherical morphology. The Electron Diffraction pattern (ED) showed polycrystalline nature of the AgNPs. SEM analysis also confirmed circular and spherical morphology of the AgNPs with a slight agglomeration, while SEM-EDX revealed the composition of the matrix to be 51.73% oxygen (O), 5.66% Carbon (C), 16.75% sodium-(Na) and 25.86% silver (Ag). FT-IR spectrograph showed strong peaks at ranges of 400-4000 per cm that confirms presence of different functional groups viz., O-H, C-H and C꞊C. The bioefficacy of AgNPs against O. coffeae at different concentration viz., 100 ppm, 150 ppm, 200 ppm, 250 ppm and 300 ppm and dosage viz., 0.1, 0.5, 1.0, 2.5, 5.0, and 10.0 ml/lit of water as compared with the standard checks viz., azadirachtin 10000 ppm @ 3.0 ml/lit of water and 3.0% P. thyrsiflorus crude extract solution @ 3.0 ml/lit of water in terms of adult mortality, ovicidal and antiovipositional toxicity at different time interval viz., 6, 12, 24, 48, 72 and 96 hours after treatment (HAT) revealed the highest of 100.0% adult mortality of O. coffeae at 200 ppm and 250 ppm at the dosage of 10.0 ml/lit and at 300 ppm at a dosage of 5.0 ml/lit. The lowest LC50 value of 0.10% for adults of O. coffeae was recorded at 200 ppm after 96 hours of treatment. The highest ovicidal activity against O. coffeae was recorded at 300 ppm concentration @ 10.0 ml/lit causing the lowest egg hatching (40.13%). The lowest LC50 value (1.63%) in terms of ovicidal effect against O. coffeae was recorded at 300 ppm of the AgNPs. The highest hatching reduction of 54.13% was recorded at 300 ppm concentration of AgNPs @ 10.0 ml/lit against O. coffeae. At 300 ppm concentration, AgNPs recorded the lowest fecundity of O. coffeae recording only 2.57 Nos. of eggs laid per female per day. The present experimentation confirmed the effectiveness of biosynthesized AgNPs as an acaricidal, ovicidal and antiovipositional agent for the management of O. coffeae, showing promise for utilization as a component of integrated tea pest management strategy.