Effect of weather variabilities on dispersion pattern of Nilaparvata lugens (Stål) (Homoptera: Delphacidae) in paddy field

Field experiments were conducted to find out the impact of weather factors and crop phenological stages on the dispersion pattern of brown planthopper (BPH), Nilaparvata lugens (Stål) in paddy during kharif 2019 and 2020 at three paddy crop phenological stages like the active tillering stage (IV week of July to III week of August), panicle bearing and grain filling stage (IV week of August to III week of October) and grain maturity stage (IV week of October to IV week of November). Weather factors in relation with mean BPH population were subjected to multiple regression and correlation analysis. The dispersion patterns were studied by regression models using Index of dispersion, Elliott’s law, Taylor’s Power Law and Iwao’s patchiness regression model. Maximum population of BPH was observed during panicle bearing and grain filling stage at 108 days after transplanting. The BPH counts were fitted to negative binomial which indicated aggregated distribution in the field and most of the weather parameters like temperature, evening relative humidity and wind speed is negatively correlated during this stage. During active tillering and grain maturity stage, Poisson distribution pattern of BPH population in the field was observed which showed random distribution.