Influence of Abiotic Factors on the Population Dynamics and Species Composition of Stem Borer Complex in Rice Ecosystem

Abstract

A field experiment was carried out at the Murjhad Research Farm, College of Agriculture, Balaghat in Madhya pradesh during Kharif 2022 and Kharif 2023 to ascertain the population dynamics of stem borer complex, their relative abundance and correlation with abiotic factors in order to propose ecologically and financially feasible measures. Results pertaining to the dynamics of species composition of stem borers of rice reveal that all the three species of stem borer of rice viz., yellow stem borer, Scirpophaga incertulas (Walker), pink stem borer, Sesamia inferens (Walker), white stem borer, Scirpophaga innotata (Walker) were prevalent during the crop season. The pooled data of the total population of stem borer complex observed during the 30th SMW was 8.0 larvae/ 20 hills attaining two peaks, the first peak during the 36th SMW (69.0 larvae/ 20 hills) and the second peak during the 42nd SMW (96.0 larvae/ 20 hills) and thereafter, the population started decreasing and reached 65.0 larvae/ 20 hills during the 43rd SMW and it disappears at the time of harvest. The per cent dead heart incidence was first observed during the 30th SMW (2.43% dead hearts) with its peak during the 36th SMW (14.84% dead hearts) and thereafter, it started decreasing and reached 5.06 per cent dead hearts during the 38th SMW and further, it disappears. The per cent white ears incidence was first observed during the 37th SMW (1.30 % white ears) with its peak during the 42nd SMW (21.52% white ears) and thereafter, it started decreasing and reached 9.24 per cent white ears during the 43rd SMW and further, it disappears. The pooled data revealed that a total of 654.5 larvae stem borer complex were observed throughout the crop growth. Among them, 467 larvae of Scirpophaga incertulas were observed comprising 71.35 per cent, Sesamia inferens population was 110.0 larvae comprising 16.81 per cent and Scirpophaga innotata population was 77.5 larvae comprising 11.84 per cent among the stem borer complex. The data revealed that population of Scirpophaga incertulas was found significantly positive correlated (r= 0.617) with sunshine hours and significantly negative correlated with minimum temperature (r= -0.553). The population of Sesamia inferens was found significantly positive correlated (r= 0.613) with sunshine hours. The larval population of Scirpophaga innotata was not found significant with any weather parameter.  The per cent dead heart was found significantly positive correlated with minimum temperature, morning relative humidity and evening humidity (r= 0.550, 0.662 and 0.633, respectively). The per cent white ear was found significantly positive correlated with maximum temperature and sunshine hours (r= 0.535 and 0.627, respectively) and significantly negative correlated with minimum temperature, morning relative humidity, evening relative humidity and evaporation (r= -0.658, -0.689, -0.703 and 0.819, respectively).