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Atmospheric temperature increases along with increasing atmospheric CO2 concentration. This is a major concern for agroecosystems. Although the impact of an elevated temperature or increased CO2 has been widely reported, there are few studies investigating the combined effect of these two environmental factors on plant-insect interactions. In this study, plant responses (phenological traits, defensive enzyme activity, secondary compounds, defense-related gene expression and phytohormone) of Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae) -susceptible and resistant rice under various conditions (environment, soil type, variety, C. medinalis infestation) were used to examine the rice-C. medinalis interaction. The results showed that leaf chlorophyll content and trichome density in rice were variety-dependent. Plant defensive enzyme activities were affected environment, variety, or C. medinalis infestation. In addition, total phenolic content of rice leaves was decreased by elevated CO2 and temperature and C. medinalis infestation. Defense-related gene expression patterns were affected by environment, soil type, or C. medinalis infestation. Abscisic acid and salicylic acid content were decreased by C. medinalis infestation. However, jasmonic acid content was increased by C. medinalis infestation. Furthermore, under elevated CO2 and temperature, rice plants had higher abscisic acid content than plants under ambient conditions. The adult morphological traits of C. medinalis also were affected by environment. Under elevated CO2 and temperature, C. medinalis adults had greater body length in the second and third generations. Taken together these results indicated that elevated CO2 and temperature not only affects plants but also the specialized insects that feed on them.

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