Saikia, MonimalaBoro, Jil2024-09-202024-09-202023https://krishikosh.egranth.ac.in/handle/1/5810214743The study on “Diversity and seasonal incidence of sucking insect pests infesting som (Persea bombycina (King ex Hook. fil.) Kosterm) and their management” was carried out during 2021-22 at Assam Agricultural University, Jorhat. A total of four species of sucking insect pests belonging to 2 orders and 4 families were recorded during the study period. They were Schizoneuraphis himalayensis (Ghosh & Raychaudhuri), Empoasca sp, Chionaspis sp. and Selenothrips rubrocinctus (Giard). Chionaspis sp. and S. rubrocinctus were recorded for the first time in muga ecosystem. S. himalayenis was active from May to 2nd week of August, 2022, and from 12th March 2023 to May, 2023, with its peak population on 21st of May, 2023. During 2022, Empoasca sp. was observed from middle of June to early September while, during 2023 it was observed from late April to May, with its peak population on 31st of July, 2022. Chionaspis sp. population was recorded from late May to 3nd week of November, 2022, again it was observed from 2nd week of May, 2023 onwards, with its peak population on 23rd of October, 2022. S. rubrocinctus was active from middle of September, 2022 to early January, 2023, with its peak population on 30th of October. Among the recorded sucking insect pests, the highest leaf infestation among the four recorded insect pests was caused by S. himalayensis (52.40%) during May, followed by Chionaspis sp. and S. rubrocinctus during October, and Empoasca sp. during July. S. himalayensis population had significant positive correlation with maximum temperature, minimum temperature, total rainfall, number of rainy days and wind speed, while morning relative humidity had a significant negative correlation on som plant. Empoasca sp. population on som plant showed significant positive correlation with maximum temperature, minimum temperature and wind speed, while morning relative humidity showed a significant negative correlation. Chionaspis sp. population on som plant had significant positive correlation with maximum temperature and minimum temperature, while morning relative humidity showed a significant negative correlation. S. rubrocinctus population showed significant positive correlation with maximum temperature, while morning relative humidity, evening relative humidity total rainfall and number of rainy day showed a significant negative correlation on som plant during the study period. The combined effect of all the weather parameters influenced 38% variation on S. himalayensis population, whereas the cumulative effect of all the weather parameters on population of Empoasca sp. Chionaspis sp. and S. rubrocinctus were 26%, 50% and 66%, respectively. Among the recorded insects S. himalayensis was found to be the most abundant (63.27%) while, the least abundant (8.77%) was Empoasca sp. DNA analysis of all the collected aphid samples produced a 5´ COI amplified region of approximately 700 base pairs. The sample collected from Kokrajhar showed 96.23% similarity with sequence of Macrosiphum sp., while sample collected from Lakhimpur district showed 92.31% similarity with the reported sequence of Szhizaphis graminum whereas, samples collected from Jorhat and Karbi Anglong district showed 91.25% similarity with the reported sequence of Diuraphis noxius. The present study revealed that the LC50 values of the aqueous extract of P. thyrsiformis, C. odorata, A. marmelos and A. indica were 1.04%, 1.07%, 0.98% and 0.57%, respectively after 72 HAT. The order of toxicity with respect to the LC50 values after 72 hours of treatment was A. indica > A. marmelos > P. thyrsiformis > C. odorata.EnglishThesis