Simulation of rice brown planthopper, Nilaparvata lugens (Stal.) population and crop-pest interactions to assess climate change impact

Brown planthopper (BPH), Nilaparvata lugens (Stal.) development studied at six constant temperatures, 19, 22, 25, 28, 31 and 33 ±1 °C on rice plants revealed that developmental period from egg hatching to adult longevity decreased from 46.8 to 18.4 days as temperature increased from 19 to 31 °C. Through regression of development rate on temperature, thermal constant of small nymph (1st-2nd instar), large nymph (3rd–5th instar) and adult were determined to be 126.6, 140.8 and 161.3 degree days (DD), respectively with corresponding development threshold being 8.8, 9.5 and 9.6 °C. A thermal constant-based mechanistic-hemimetabolous-population model was adapted for BPH and linked with InfoCrop, a crop simulation model to simulate climate change impact on both the pest population and crop-pest interactions. The model was validated with field data at New Delhi and Aduthurai (Tamil Nadu, India), (R ²?=?0.96, RMSE?=?1.87 %). Climate-change-impact assessment through coupled BPH-InfoCrop model, in the light of the projected climate-change scenario for Indian subcontinent, showed a decline of 3.5 and 9.3–14 % in the BPH population by 2020 and 2050, respectively, during the rainy season at New Delhi, while the pest population exhibited only a small decline of 2.1–3.5 % during the winter at Aduthurai by 2050. BPH population decline is attributed to reduction in fecundity and survival by simulation model, which otherwise was not possible to account for with an empirical model. Concomitant to its population decline, BPH-induced yield loss also indicated a declining trend with temperature rise. However, the study considered the effect of only CO₂ and temperature rise on the BPH population and crop yield, and not that of probable changes in feeding rate and adaptive capacity of the pest.