Kalita, SurajitMahanta, Ritushree2020-12-282020-12-282020-09https://krishikosh.egranth.ac.in/handle/1/5810157449The experiment on bioefficacy of Annona squamosa (L.) (Family: Annonaceae), Adhatoda vasica (L.) (Family: Acanthaceae), Cascabela thevetia (L.) Lippold (Family: Apocynaceae), Datura stramonium (L.) (Family: Solanaceae) and Lawsonia inermis (L.) (Family: Lythraceae) leaf extracts conducted at Department of Entomology, Assam Agricultural University, Jorhat during 2018-20 revealed a dose- and time-dependent mortality of red spider mite (RSM), Oligonychus coffeae Nietner (Tetranychidae: Acarina) and tea mosquito bug (TMB), Helopeltis theivora Waterhouse (Miridae: Hemiptera) attacking tea plantation. The leaves of the selected insecticidal plants were collected from the Jorhat district of Assam; which were later macerated and extracted with standard procedure in distilled water on weight/volume basis for preparation of desired concentrations through serial dilution method viz., 0.1%, 0.5%, 0.75%, 1.0%, 2.5%, 5.0%, 7.5%, 10.0%. Neem Seed Kernel Extract (NSKE) 0.15% EC 2 5 ml/litre of water as standard check along with a control (water) were also taken for toxicity comparison. The treatments were replicated thrice and the data on adult mortality were recorded at 6, 12, 24, 48 and 72 hours after treatment (HAT). Moreover, plant extracts at different concentrations were also tested for ovicidal activity against O. coffeae. Tea leaves were also tested for any change in biochemical properties of tea leaves after application of botanicals to control H. theivora and O. coffeae at Phytochemistry Laboratory, Department of Biochemistry & Agricultural Chemistry, AAU, Jorhat during 2018-20. Best three plant extracts showing lowest LC50 values against the test insects were considered for biochemical investigation and data were recorded at 1,3, 5 and 10 days after spraying (DAS) of botanicals with three replications. The results on bioefficacy revealed the strong acaricidal properties of D. stramonium recording 90.00% mortality of O. coffeae adults, while L. inermis has been found to be having strong insecticidal properties against H. theivora adults recording 80.00% mortality at 72 hours after treatment (HAT). The water extract of D. stramonium had the highest ovicidal properties causing complete inhibition of hatching of O. coffeae eggs even upto 5.00% concentration as against 91.32% hatching in the control, which was followed by A. vasica recording 25.93% hatching at 5.00% concentration as compared to 93.03% hatching in the control. 6 The order of toxicity of botanicals against O. coffeae in terms of LC50 values was D. stramonium (0.270%)>A. vasica (1.979%) >L. inermis (2.085%) > C. thevetia (3.740%) > A. squamosa (3.942%); while the order of toxicity in case of H. theivora was found to be L. inermis (1.052%)>D. stramonium (2.228%) >C. thevetia (2.296%) >A. vasica (2.644%) >A. squamosa (4.534%). The best three botanicals based on their LC50 values viz., Lawsonia inermis (1.052%), Datura stramonium (2.228%) and Cascabela thevetia (2.296%) for H. theivora and for O. coffeae the botanicals viz., Datura stramonium (0.270%), Adhatoda vasica (1.979%) and Lawsonia inermis (2.085%) were tested for biochemical parameters including chlorophyll a & b, carotenoids, reducing sugar and polyphenols along with healthy leaf sample and found that the reducing sugar content in TMB and RSM infested tea leaves decreased upon application of D. stramonium leaf water extracts to 1.592 mg/100g and 3.477 mg/100g, respectively at 10 DAS as compared to control (6.566 mg/100g & 5.487 mg/100g respectively). Whereas, the polyphenol content in TMB and RSM infested tea leaves decreased upon application of treatment with L. inermis and D. stramonium leaf water extracts to 3.967 mg/100g and 3.247 mg/100g, respectively on 10 DAS as compared to the control (8.470 mg/100g & 6.773 mg/100g respectively). The chlorophyll a, chlorophyll b and carotenoids contents in both TMB and RSM infested tea leaves was found to have decreased upon application of D. stramonium leaf extracts.EnglishThesis