Impact of Elevated CO 2 on Oryza sativa Phenology and Brown Planthopper, Nilaparvata lugens (Hemiptera:Delphacidae) Population

The impact of elevated CO₂ (570 ± 25 ppm) on brown planthopper, Nilaparvata lugens (Stal) and Pusa Basmati 1401 rice in comparison to ambient CO₂ was studied in open top chambers (OTCs) during the rainy seasons of 2013 and 2014. Crop canopy circumference was higher (13.1–16.8 cm) under elevated CO₂ when compared to ambient CO₂ (10.3–13.1 cm) during different rice phenological stages indicating the positive influence of elevated CO₂. In addition, elevated CO₂ exhibited a positive effect on rice plants through increase in tiller number (17.6%), reproductive tiller number (16.2%), number of seeds/panicle (15.1%) and thousand grains weight (10.8%) that resulted in higher grain yield (15%) when compared to ambient CO₂. Elevated CO₂ also exhibited a positive effect on brown planthopper population through increase in fecundity (29% and 31.6%) which resulted in a significant increase in its population to 150.3 ± 16.4 and 97.7 ± 8.7 hoppers/hill at peak incidence during 2013 and 2014 respectively, when compared to the corresponding 49.1 ± 9.3 and 43.7 ± 7.0 hoppers/hill under ambient CO₂. Moreover, brown planthopper females excreted more honeydew (68.2% and 72.3%) under elevated CO₂ over ambient CO₂ during both years. However, elevated CO₂ caused reduction in the longevity of females (23.9–27.4%) during both years and male longevity (24.1%) during 2013. Despite the positive effect, rice crops suffered higher yield loss under elevated CO₂ (29.9–34.9%) due to increased brown planthopper infestation coupled with higher sucking rate due to reduced nitrogen level under elevated CO₂ compared to ambient CO₂ (17–23.1%) during 2013 and 2014.