Interactive Effects of Elevated CO2 and Temperature on Rice Planthopper,Nilaparvata lugens

It is predicted that the current atmospheric CO₂ concentration will be doubled and global mean temperature will increase by 1.5–6°C by the end of this century. Although a number of studies have addressed the separate effects of CO₂ and temperature on plant-insect interactions, few have concerned with their combined impacts. In the current study, a factorial experiment was carried out to examine the effect of a doubling CO₂ concentration and a 3°C temperature increase on a complete generation of the brown planthopper (Nilaparvata lugens) on rice (Oryza sativa). Both elevated CO₂ and temperature increased rice stem height and biomass of stem parts. Leaf chlorophyll content increased under elevated CO₂, but only in ambient temperature treatment. Water content of stem parts was reduced under elevated temperature, but only when coupled with elevated CO₂. Elevated CO₂ alone increased biomass of root and elevated temperature alone enhanced leaf area and reduced ratio of root to stem parts. Brown planthopper (BPH) nymphal development was accelerated, and weight of and honeydew excretion by the F₁ adults was reduced under elevated temperature only. Longevity of brachypterous females was affected by a significant interaction between CO₂ and temperature. At elevated temperature, CO₂ had no effect on female longevity, but at ambient temperature, the females lived shorter under elevated CO₂. Female fecundity was higher at elevated than at ambient temperature and higher at elevated CO₂ than at ambient CO₂. These results indicate that the combined effects of elevated temperature and CO₂ may enhance the brown planthopper population size.