Impact of elevated CO2on Oryza sativa phenology and brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae) population

The impact of elevated CO2 (570 ± 25 ppm) on brown planthopper, Nilaparvata lugens (Stål) 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.