Population dynamics of the rice yellow stem borer Scirpophaga incertulas (Walker) in Assam

A study on the population dynamics of rice stem borer Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae) in the boro season in Cachar, Assam during 2012 and 2013 on var. IR 36, revealed that the peak incidence of adults was during the 2^nd week of February (3.6±0.27 nos./quadrat). As regards larva, the peak incidence was (4.1±0.16 nos./hill; var. Balam) in the middle of April. In case of adults, significant (p<0.05) correlations with weather factors was observed, except in Balam (‘F’=1.16, p>0.05) and Chocolate (‘F’=0.11, p>0.05); on the adults temperature and rainfall had an insignificant effect (p>0.05) while relative humidity had significant effect (p<0.05) effect on var. Aizong (t= -2.76,p<0.05 for adult; t= -1.73,p<0.05 for larva) and IR-36 (t= -2.25, p<0.05 for adult; t= -2.88, p<0.05 for larva).