Impact of elevated CO₂ on Nilaparvata lugens (Stal), rice crop and feeding of Pardosa pseudoannulata

Effect of elevated CO₂ on brown planthopper Nilaparvata lugens (Stal.) population was analyzed under open top chamber (OTC) at elevated CO₂ (570 ± 25 ppm) compared to ambient CO₂ (400± 25 ppm) during kharif 2015 and 2016. Elevated CO₂ exhibited positive effect on BPH that resulted in doubling of its population at peak incidence (120.2± 14.7 hoppers/hill) than ambient CO₂ (61.8± 13.55 hoppers/hill) during 2015. Similarly, during 2016, BPH peak population under elevated CO₂ was observed to be higher (149.2 ± 22.95 hoppers/hill) than ambient CO₂ (93.2± 8.55 hoppers/hill). Elevated CO₂ exhibited nutritive effect on uninfested rice plants through 6–8% increase in grain yield compared to ambient CO₂. However, despite the nutritive effect, rice plants under elevated CO₂ condition suffered higher yield loss (30–31.9%) due to more BPH population compared to plants grown under ambient CO₂ that had 17.7–18.5% yield loss. Feeding behaviour of wolf spider, in relation to prey densities of 3^rd-4^th instar BPH nymphs was observed in microcosm under elevated and ambient CO₂. Under elevated CO₂, the predation rate (5.67±0.34 to 12.34±1.33 hoppers/predator) was slightly higher than microcosm (4.67±0.33 to 10.0±1.0 hoppers/predator).