Effect of biotic and abiotic factors on the population of brown planthopper, Nilaparvata lugens (Stal) in relation to two varieties and planting dates

A field experiment on population dynamics of brown planthopper was conducted during Kharif, 2011 and 2012 at CCS HAU Rice Research Station, Kaul, Kaithal (Haryana). During 2011, the population of BPH was positively correlated (r= 0.697) with parasitoid populations in June transplanting (D1) while, in July transplanting (D2), there was a positive correlation with spiders (r= 0.632), mirid bugs (r= 0.666) and sun shine hours (r = 0.629). The population of BPH was highly positive correlated with spiders (r= 0.758), parasitoids (r= 0.780) and highly negative correlated with Tmin (r= -0.818) and rainfall (r= -0.760) on variety CSR 30 planted in June during 2012 and none of the abiotic and biotic factors showed any significant impact on BPH population in D2 during 2012. Significant effect of biotic and abiotic factors was recorded on population of BPH during 2011 on variety PR 114 planted in June. The population of BPH was positively correlated with spiders (r=0.662) and mirid bug (r= 0.955) while, Tmin (r= -0.844) and rainfall (r= -0.674) were negatively correlated in D1 of cultivar PR 114 during 2011. In July transplanting (D2), the spiders (r= 0.688) and mirid bugs (r= 0.903) and SSH (r=0.629) were highly positive correlated while, Tmin (r=-0.812) and rainfall (r= -0.685) had negative impact on population BPH. However, during 2012, none of the variables showed any relation with BPH population.