A field experiment with elevated atmospheric CO2-mediated changes to C4 crop-herbivore interactions

Area of Science:

• Agricultural Science
• Entomology
• Climate Change Biology

Background:

• Rising atmospheric CO2 levels present a significant environmental challenge.
• Maize (Zea mays) is a vital global crop susceptible to insect pests like the Asian corn borer (Ostrinia furnacalis).
• Understanding plant-insect interactions under future climate conditions is crucial for food security.

Purpose of the Study:

• To investigate the impact of elevated CO2 on maize growth and nutritional quality.
• To assess the effects of elevated CO2 on the Asian corn borer (ACB) and its interaction with maize.
• To determine how elevated CO2 influences plant defense and insect herbivory.

Main Methods:

• Maize plants were grown in open-top chambers under ambient and elevated CO2 concentrations (550 and 750 μl/l).
• Plants were artificially infested with Asian corn borer (ACB) larvae.
• Plant growth parameters, nutritional content (nitrogen, TNC:N ratio), ACB weight gain, survival, and plant damage were measured.

Main Results:

• Elevated CO2 increased maize plant height and kernel number but decreased plant nitrogen content and increased TNC:N ratios.
• ACB larval weight gain declined under elevated CO2, and overwintering larvae showed a lower supercooling point.
• Plant damage by ACB did not differ significantly across CO2 treatments, suggesting a 'masking' effect of increased plant biomass.

Conclusions:

• Elevated CO2 enhances maize biomass accumulation (the "air-fertilizer" effect) but induces nutritional deficiencies.
• The reduced nutritional quality of maize under elevated CO2 adversely affects ACB fitness and survival.
• Despite reduced insect fitness, elevated CO2 may offset visible plant damage through increased plant growth, highlighting complex plant-insect dynamics under climate change.