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Elevated atmospheric carbon dioxide affects crop herbivory by insects.
Hamilton, Jason*,1, Dermody, Orla2, Aldea, Mihai1, Zangerl, Arthur2, Berenbaum, May2, Rogers, Alistair3, DeLucia, Evan2, 1 Ithaca College, Ithaca, NY email@example.com University of Illinois at Urbana-Champaign, Urbana, IL3 Brookhaven National Laboratory, Upton, NY
ABSTRACT- Human activity is rapidly altering the chemistry of the troposphere in ways that may have important effects on chemical composition of leaves. These changes in leaf chemistry will potentially affect the interactions between plants and insect herbivores. At the University of Illinois SoyFACE (Free-Air Concentration Enrichment) facility, experimental plots of soybean (Glycine max) were exposed to ambient air, elevated CO2 (550 ppm), or elevated ozone (1.2 X ambient). In July and August 2002, we measured levels of insect herbivory, insect populations and changes in leaf chemistry. In July, elevated CO2 more than doubled the amount of leaf tissue consumed by herbivores (ambient losses 4.5%; elevated losses 10.6%), whereas elevated ozone had no measurable effect (5.9%). In August, overall levels of herbivory were much lower with no significant difference between ambient and elevated CO2 plots. In July, the main insect causing this damage was the introduced Japanese beetle (Popillia japonica), with significantly larger populations in the elevated CO2 plots compared to control. Measurements of leaf tissue chemical composition showed large increases in three known feeding stimulants of Japanese beetle (sucrose, glucose and fructose). Feeding trials confirmed that Japanese beetles consume more tissue from soybean leaves grown under elevated CO2 conditions. These results suggest that changes in tropospheric chemistry caused by human activities may increase crop damage by insect herbivores in the future.
Key words: Glycine max, herbivory, elevated carbon dioxide, global change