Response of multiple generations of cotton bollworm Helicoverpa armigera Hübner, feeding on spring wheat, to elevated CO2

Abstract:  The growth, development and consumption of three successive generations of cotton bollworm, Helicoverpa armigera (Hübner), reared on milky grains of spring wheat grown under elevated CO₂ (double-ambient vs. ambient) in open-top chambers (OTCs) were examined. Decreases in protein, total amino acid, water and nitrogen content, and increases in total non-structure carbohydrates (TNCs) and ratio of TNC : nitrogen were found in wheat milky grains grown under elevated CO₂ conditions. Changes in quality of wheat grains affected the growth, development and food utilization of H. armigera . Significantly longer larval lifespan for the third generation and lower pupal weight for all generations were observed in cotton bollworm fed on milky grains of spring wheat grown under elevated CO₂ conditions. Bollworm fecundity was significantly decreased for the second and third generations under elevated CO₂ levels. The consumption, frass per larva and relative consumption rate significantly increased in elevated CO₂ compared with ambient CO₂ conditions. However, the potential population consumption was significant reduced by elevated CO₂ in the second and third generations. The results of this study indicate that elevated CO₂ levels adversely affect grain quality, resulting in consistently increased consumption per larva for a longer period to produce less fecund bollworm through generations, suggesting that net damage of cotton bollworm on wheat will be less under elevated atmospheric CO₂ levels because increased consumption is offset by slower development and reduced fecundity.