Ahmad, Md. AbbasChoudhury, Srishti2022-12-312022-12-312022M/Ento./075/2020-21https://krishikosh.egranth.ac.in/handle/1/5810190892Out of the several pests observed in the boro rice ecosystem at Pusa, the yellow stem borer, leaf folder, whorl maggot and gundhi bug were observed to cause maximum damage to the crop. The maximum incidence of dead heart and white ears was seen during the 14th standard week of April and 20th standard week of May respectively. Dead heart incidence had a significant negative correlation with rainfall, whereas white ear head incidence was seen to have a significant positive correlation with rainfall, minimum temperature and relative humidity. The leaf folder incidence peaked during the 17th standard week of April with 62.93 per cent incidence and represented a positive and significant relation with respect to rainfall and bright sunshine hours. In case of whorl maggot, maximum incidence of 3.43% was recorded during the 16th standard week of April and there was a negative but significant relationship with minimum temperature as well as relative humidity in the evening. Gundhi bug incidence reached its peak point (4.05%) at the 21st standard week of May and showed a significant positive correlation with minimum temperature. The sweep net and handpicking methods used to capture natural enemies revealed that lady bird beetles, mirid bugs, dragonfly, damselfly, spiders and rove beetles were the dominant ones during Rabi 2021-22 in the boro rice production ii system. Among them, lady bird beetles had the highest relative abundance (30.07%), followed by spiders (16.70%), rove beetles (14.59%), damselfly (14.05%), dragonfly (13.64%) and mirid bugs (10.93%). The number of lady bird beetles, dragonfly and damselfly were observed to be the maximum during the months of March to April whereas spiders, mirid bugs and rove beetles reached maximum numbers during May. Representative samples of water after the first application, field soil and paddy leaves after the second application whereas that of straw, grain and husk at the harvesting period were collected and analyzed using modified QuEChERS technique. In water, at 0 day (2hrs after application) after the first application, the mean initial residue was 0.03 mg/kg at double dose (90 g a.i/ha) whereas at 45 g a.i./ha and 60 g a.i/ha, the residues were below the LOQ (0.01 mg/kg) and 1 day after applying the insecticide, the insecticide was undetectable in case of all the treatments. In soil samples, maximum residues were found at 0 day (2hrs after second application) for all the doses. The residues dissipated below the LOQ (0.05 mg/kg) after 15 days of the second application in case of the recommended dose. On the other hand, for 1.5 times the recommended dose and double dose, the amount of residues reached below the LOQ (0.05 mg/kg) after 30 days. In case of paddy leaves, the maximum level of residue was found after 3 days of the second application. After fifteen days of second application, residues in leaves were found to move below the LOQ (0.05 mg/kg) for 45 g a.i/ha as well as 60 g a.i/ha. However, at the double dose (90 g a.i/ha) the residues were found to be undetectable (<0.05 mg/kg) after 30 days of second application. Residue level was found to be below the limit of quantification (0.05mg/kg) in the harvest samples of grains, straw and husk. Hence, imidacloprid 0.3G wasn‟t found to cause issues of residual toxicity in the paddy production ecosystem.EnglishThesis