Response of spring crops and associated aphids to elevated atmospheric CO₂ concentrations

Abstract

Having evolved a parasitic relation to their host plants, aphids may serve as indicators of plant responses to environmental changes. The present rise in atmospheric CO_{2 concentrations is expected to alter plant leaf chemistry and may thus alter host plant – aphid relations. We involved a climate chamber system and used bird cherry-oat aphid (Rhopalosiphum padi L.) and green peach aphid (Myzus persicae S.) and their respective host plants, spring wheat (Triticum aestivum L. cv. “Triso”) and oilseed rape (Brassica napus cv. “Campino”), to elucidate the effects of atmospheric CO2 enrichment on such bitrophic systems. Spring wheat grown at elevated CO2 (600 ppm) generally had greater above ground biomass than plants grown at ambient CO2 (400 ppm). Bird cherry-oat aphid infestation resulted in reduced spring wheat above ground biomass compared to the non-infested control. Relative crop growth rate (RGR) was increased by elevated CO2. In our study, the relative developmental stage (rDS) and intrinsic rate of increase (rm) of the aphids was only slightly and non-signifi cantly increased under elevated atmospheric CO2 conditions. The response of aphid weight and RGR to elevated CO2 differed, increasing by 24% and 18.2% for bird cherry-oat aphid and decreasing by 12% and 12.5% for green peach aphid, respectively. Aphids reared on spring wheat at elevated CO2 had a shorter lifespan, whereas the opposite effect was found for aphids reared on oilseed rape. The average number of nymphs of the two pest species showed both an increase under elevated CO2. No consistent picture emerges from these findings, and further investigation on host – aphid relations under changing atmospheric conditions such as CO2 enrichment appear necessary.}