Elevated carbon dioxide reduces Aphis gossypii intrinsic increase rates without affecting Aphidius colemani parasitism rate

Abstract

Abstract Climate change could increase pest pressure, due to changes in insect distribution and phenology, affecting herbivore-parasitoids interactions and consequently, the efficacy of biological control of crop pests. Elevated carbon dioxide (eCO2) concentration directly affects plant growth, physiology and biochemistry, subsequently influencing herbivore insects and higher trophic levels. In this study, we analysed the effect of eCO2 on the individual fitness of Aphis gossypii Glover (Hemiptera: Aphididae) and on the performance of its parasitoid Aphidius colemani Vierick (Hymenoptera: Braconidae), both reared for two successive generations on melon plants (Cucumis melo L., Cucurbitaceae), previous acclimated during two or six weeks to different CO2 levels, eCO2 (700 ppm) or ambient CO2 (400 ppm). There was a significant impact of eCO2 on aphid performance, prolonging its development time and decreasing its fecundity, negatively affecting the intrinsic rate of natural increase of the two generations of A. gossypii grown under eCO2. There was lower proportion of parasitoids emergence (i.e. pupal survivorship) in first generation A. colemani grown under eCO2. However, parasitism rate, emergence percentages by sex and the overall development time, remained unchanged due to the effect of eCO2 for the two generations of A. colemani. Our research suggests that the effects of eCO2 on the tritrophic interaction studied could reduce herbivore infestation by decreasing its growth rate. Despite the parasitism efficiency is maintained, in the long term A. colemani will not easily find A. gossyppi for parasitism and their populations could be compromised, although less than other parasitoids with greater host specificity.