Impact of Elevated CO2 on Growth and Development of Multiple Generations of Beet armyworm, Spodoptera exigua (Noctuidae: Lepidoptera) on Chickpea

Abstract

Rising atmospheric carbon dioxide (CO₂) can alter host-plant chemistry and thereby affect herbivorous insects across generations. This study evaluated the effects of ambient CO₂ (aCO₂; 380 ± 25 ppm) and elevated CO₂ (eCO₂; 550 ± 25 ppm) on chickpea foliar biochemistry and the growth, development, feeding indices, and fecundity of Spodoptera exigua over four successive generations. Chickpea plants were grown in open-top chambers, and larvae were reared on foliage produced under the corresponding CO₂ conditions. Compared with aCO₂, eCO₂ reduced leaf nitrogen, protein, and amino acid contents while increasing carbon, the C:N ratio, tannins, total soluble sugars, starch, and carbohydrates. Larvae feeding on eCO₂-grown foliage consumed more leaf material, produced more faecal matter, and showed greater larval weight gain. Approximate digestibility and relative consumption rate increased, whereas the efficiencies of conversion of ingested and digested food and the relative growth rate decreased. Larval and pupal development was prolonged under eCO₂, and the total developmental period increased. Pupal weight and fecundity were lower in insects reared on eCO₂-grown foliage than in those reared under aCO₂ conditions. These responses were observed across four generations, indicating that CO₂-mediated changes in chickpea foliage quality can persistently influence S. exigua performance. The findings suggest that elevated CO₂ may alter pest development and feeding behaviour through host-plant-mediated effects.