Author(s):

Divya Bharathi T, Srinivasa Rao M and Krishnayya PV

Abstract: The objective of this study was to examine the direct effects of two different CO₂ concentrations (380 ppm and 550 ppm) on the life table parameters of Spodoptera exigua at six temperatures (20, 25, 27, 30, 33 and 35 °C) fed on chickpea foliage. The life history and fitness of S. exigua was analyzed using two-sex life table. Our results showed significantly the development time (days) of S. exigua (egg to adult) declined with increase in temperature and was more evident under elevated CO₂ conditions. Additionally, the fecundity of S. exigua was lower under elevated CO₂ than ambient CO₂ conditions across the temperatures. Finite (l) and intrinsic rates of increase (rm), net reproductive rate (Ro), gross reproductive rate (GRR), mean generation time (T) and doubling time (DT) of S. exigua varied significantly with temperature and CO₂ and were found to have quadratic relationships with temperature. The reduction of ‘T’ was noticed from a maximum of 49.52 days at 20 °C to minimum of 20.20 days at 35 °C under elevated CO₂ conditions. According to population projections, a much smaller total population size would be expected in an elevated CO₂ atmosphere due to lower fecundity and higher mortality compared with ambient CO₂ conditions.

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