Effects of different atmospheric CO2 concentrations and soil moistures on the populations of bird cherry-oat aphid (Rhopalosiphum padi) feeding on spring wheat

Spring wheat plants were grown in pots at three CO2 concentrations (350, 550 and 700 ppm) and three soil water levels (40, 60 and 80% of field water capacity) in field open top chambers and were infested with bird cherry-oat aphids (Rhopalosiphum padi Linnaeus). Aphid population dynamics were recorded throughout the growing season and analysis of the chemical composition of spring wheat leaves was conducted at the same time. Results showed that: (1) Aphid populations increased with raised atmospheric CO2 concentrations. (2) The aphid populations showed different responses to different CO2 concentrations. The population size, population growth rate and population density found under the 350 ppm CO2 treatment was far less than those recorded under the 550 and 700 ppm CO2 treatments. The population size, population growth rate and population density recorded under the 700 ppm CO2 treatment was slightly higher than those recorded under the 550 ppm CO2 treatment. (3) The effect of CO2 concentration on the aphid population was correlated with soil water level. The highest aphid population size was achieved under the 60% soil water treatment. (4) Atmospheric CO2 and soil moisture had significant effects on the chemical Composition of the wheat leaves. (5) Aphid population size correlated positively with the concentration of leaf water content, soluble proteins, soluble carbohydrates and starch, while correlating negatively with the concentration of DIMBOA and tannin.