Borah, D.K.Singh, Hemam Ramananda2019-05-172019-05-172017-07http://krishikosh.egranth.ac.in/handle/1/5810103599Investigation on reaction of some aromatic rice varieties against major insect pests and relationship between morphological and biochemical properties of the rice varieties with insect pest incidence and evaluation of some promising insecticides and neem based insecticides to major insect pests and their natural enemies were carried out at the Assam Agricultural University, Jorhat, during Kharif, 2013 and 2014. From the present investigation, it was found that among the 13 aromatic rice varieties screened during Kharif 2013 and 2014, none of the varieties showed resistance to stemborer. However three varieties viz. Boga Maniki Joha, Koli Joha and Ronga Joha showed Moderately Resistance during vegetative stage and Moderately Susceptible during reproductive stage. In case of case worm and leaf folder, none of the varieties were found to be resistant during the investigation. The morphological characters of the aromatic rice varieties showed non-significant correlation with the incidence of insect pests studied. In case of biochemical properties, carbohydrate showed significant positive correlation with case worm and leaf folder infestation, while non-significant positive correlation with stem borer. Nitrogen showed significant positive correlation with stem borer infestation but non-significant positive correlation to case worm and leaf folder infestation. Chlorophyll, fat and protein showed non-significant positive correlation with the entire insect pest studied. However, phenol showed significant negative correlation with stem borer and leaf folder and non-significant negative correlation with case worm. Investigation on efficacy of some insecticides revealed that Fipronil 80 WG @ 40 g a.i./ha was superior in reducing the infestation by stemborer in terms of both DH and WEH followed by Flubendiamide @ 24g a.i./ha, Lambda-Cyhalothrin @ 25g a.i./ha and Thiamethoxam @ 25g a.i./ha. In case of case worm, the percent reduction over control was highest in Flubendiamide @ 24g a.i./ha (78.31) followed by Fipronil 80WG @40g a.i./ha (75.00), Thiamethoxam @ 25g a.i./ha (69.01) and Lambda-Cyhalothrin @ 25g a.i./ha (66.12) respectively. Similarly in case of leaf folder, the present finding showed that Flubendiamide @ 24g a.i./ha was most effective and it was equally effective statistically with Thiamethoxam @ 25g a.i./ha and Fipronil 80WG @ 40g a.i./ha followed by Lamda-Cyhalothrin @ 25g a.i./ha. The highest yield was recorded in Fipronil 80WG @ 40g a.i./ha followed by Flubendiamide 39.35 SC @ 24g a.i./ha and Thiamethoxam @ 25g a.i./ha however the highest benefit-cost ratio was observed in Thiamethoxam @ 25g a.i./ha. Data on the effect of treatments on natural enemies revealed that Chlorpyriphos @ 500g a.i./ha recorded the least population of odonates and coccinellids followed by Lambda-Cyhalothrin @ 25g a.i./ha and Thiamethoxam @ 25 g a.i./ha respectively while Lambda-Cyhalothrin @ 25g a.i./ha recorded the least population in case of spider followed by Chlorpyriphos @ 500g a.i./ha and Thiamethoxam @ 25g a.i./ha respectively. Neem insecticide @ 3ml/L showed least effect on spider and coccinellids followed by Flubendiamide @ 24g a.i./ha and Spinosad @ 50g a.i./ha respectively. However Flubendiamide 24g a.i./ha showed the least effect on odonates followed by neem insecticide @ 3ml/L and Spinosad @ 50g a.i./ha respectively.ennullThesis