Exploring the Hexapod Natural Enemy Complex of West Bengal's Terai Rice Ecosystem

Abstract

Aims: The aim of this study is to investigate into the hexapod natural enemy fauna prevailing in the rice (Oryza sativa L.) ecosystem under the Terai agro-ecological region of West Bengal. Study Design: The study was conducted using the rice variety MTU 1153, cultivated under standard agronomic practices without any plant protection measures to allow natural pest and predator interactions. To assess the hexapod natural enemy complex, sweeping net sampling was employed. Sampling was performed at five predetermined 1 m² plots within the experimental field. Place and Duration of Study: Field study was carried out at the Instructional Farm of Uttar Banga Krishi Viswavidyalaya (UBKV), Pundibari, Coochbehar for consecutive two seasons viz. Kharif rice (2022) and Boro rice (2023). Methodology: Predators and parasitoids were collected by 10 sweeps per m2 area per sampling site.  Sampling began at 15 days after transplanting and continued at weekly intervals till maturity of the crop. At each designated 1 m² sampling site, 10 sweeps were conducted per sampling session to standardize collection effort and ensure consistency. The collected samples were categorized and classified based on their taxonomic orders. Results: Study revealed a diverse range of natural enemy fauna with a record of thirteen predatory and parasitic insect species belonging to seven families and three orders. Correlation coefficient (r) between the weekly captured predator/ parasitoids and the weather parameters were calculated. The population build-up Micraspis sp. was correlated negatively and significantly with minimum temperature (r = -0.775) during kharif and was positively and significantly correlated with GDD (r = 0.573) during both kharif and rabi season. Population of cardiochilinae wasp has shown a significant and positive correlation with maximum (r = 0.625) and minimum relative humidity (r = 0.622) during kharif season. Different diversity indices for kharif and rabi such as Shannon-Wiener index (2.32,2.174), Simpson’s index (0.892,0.866), Pielou’s index (0.932,0.875) and Margalef index (1.992,1.967) revealed moderately rich biodiversity of natural enemies in the rice ecosystem. Conclusion: The rice ecosystem revealed a remarkable level of diversity of natural enemies. The predators and parasitoids recorded during the experiment are well known for their multifaceted valuable role in maintaining ecological equilibrium by regulating pest population.