Assessment of yield loss in rice caused by Scirpophaga incertulas (Walk.) at Gangetic New Alluvial Zones of West Bengal, India

A field experiment was conducted in both kharif and boro season for assessment of yield losses of Scirpophaga incertulas (Walk.) in locally adopted rice cultivar IET 4786 during 2012 to 2014. Four different levels of released egg masses viz. t₁ = one egg mass/m², t₂ = two egg mass/m², t₃ = three egg mass release/ m² and t₄ = no egg mass/m² area were randomized in four replication and data were recorded at vegetative and reproductive stage respectively. Maximum percent of dead hearts subsequent white ear heads were recorded in case of 3 numbers of yellow stem borer (YSB) egg masses/m² followed by 2 numbers of YSB egg masses/m² and one number of YSB egg mass/m² during both kharif and boro season respectively. the regression equation for extent of yield reduction for dead heart (DH) was by 0.0887 units whereas for white ear (WE) was by 0.3269 units. Correlation model explains that the extent of yield loss corroborates the extent of infestation. the yield loss was calculated with respect to control which revealed that 3 numbers of YSB egg masses/m² exhibited its supremacy 35.31% followed by 2 numbers of YSB egg masses/m² (28.78%) and one numbers of YSB egg mass/m² (25.45%). A separate regression equation was developed from boro season of 2013 and 2014 where per unit increase in DH and WE caused yield reduction by 0.078 and 0.2745 units respectively. results show that the overall damage percentages were constantly increased from vegetative to reproductive stage. Here per unit increase of subsequent dead heart and white ear caused yield reduction by 0.0887, 0.3269 and 0.078, 0.275 units in kharif and boro seasons respectively and clipping of Scirpophaga incertulas (Walk.) egg masses could save at least 7.142% and 13.040% damage in a crop period.