Temperature- and CO2-dependent life table parameters of Spodoptera litura (Noctuidae: Lepidoptera) on sunflower and prediction of pest scenarios.

Predicted increase in temperature and atmospheric CO2 concentration will influence the growth of crop plants and phytophagous insects. The present study, conducted at the Central Research Institute for Dryland Agriculture, Hyderabad, India, aimed at (1) construction of life tables at six constant temperatures viz., 20, 25, 27, 30, 33, and 35 ± 0.5 °C for Spodoptera litura (Fabricius) (Noctuidae: Lepidoptera) reared on sunflower (Helianthus annus L.) grown under ambient and elevated CO2 (eCO2) (550 ppm) concentration in open top chambers and (2) prediction of the pest status in near future (NF) and distant future (DF) climate change scenarios at major sunflower growing locations of India. Significantly lower leaf nitrogen, higher carbon and higher relative proportion of carbon to nitrogen (C:N) were observed in sunflower foliage grown under eCO2 over ambient. Feeding trials conducted on sunflower foliage obtained from two CO2 conditions showed that the developmental time of S. litura (Egg to adult) declined with increase in temperature and was more evident at eCO2. Finite (λ) and intrinsic rates of increase (r(m)), net reproductive rate (Ro), mean generation time, (T) and doubling time (DT) of S. litura increased significantly with temperature up to 27-30 °C and declined with further increase in temperature. Reduction of 'T' was observed from maximum value of 58 d at 20 °C to minimum of 24.9 d at 35 °C. The DT of population was higher (5.88 d) at 20 °C and lower (3.05 d) at 30 °C temperature of eCO2. The data on these life table parameters were plotted against temperature and two nonlinear models were developed separately for each of the CO2 conditions for predicting the pest scenarios. The NF and DF scenarios temperature data of four sunflower growing locations in India is based on PRECIS A1B emission scenario. It was predicted that increased 'rm', 'λ', and 'Ro' and reduced 'T' would occur during NF and DF scenario over present period at all locations. The present results indicate that temperature and CO2 are vital in influencing the population growth of S. litura and pest incidence may possibly be higher in the future.

Response of multiple generations of semilooper, Achaea janata feeding on castor to elevated CO2.

The growth, development and consumption of four successive generations of semilooper, Achaea janato reared on castor (Ricinus communis L.) foliage grown under elevated carbon dioxide (550 and 700 parts per million ) concentrations in open top chambers were estimated at Hyderabad, India. Significantly lower leaf nitrogen, higher carbon, higher relative proportion of carbon to nitrogen (C: N) and higher polyphenols expressed in terms of tannic acid equivalents were observed in castor foliage under elevated CO2 levels. Significant influence on life history parameters of A. jonata viz., longer larval duration, increased larval survival rates and differential pupal weights in successive four generations were observed under elevated over ambient CO2 levels. The consumption per larva under elevated CO2 increased from first to fourth generation. An increase in approximate digestibility and relative consumption rate, decreased efficiency of conversion of ingested food and digested food and relative growth rate of the four generations under elevated CO2 levels was noticed. Potential population increase index was lower for successive generations under both elevated CO, over ambient. The present findings indicated that elevated CO2 levels significantly alter the quality of castor foliage resulting in higher consumption and better assimilation by larvae, slower growth and longer time to pupation besides producing less fecund adults over generations.

Impact of elevated CO2 on tobacco caterpillar, Spodoptera litura on peanut, Arachis hypogea.

If the carbon dioxide (CO(2)) concentration in the atmosphere changes in the future, as predicted, it could influence crops and insect pests. The growth and development of the tobacco caterpillar, Spodoptera litura (Fabricius) (Noctuidae: Lepidoptera), reared on peanut (Arachis hypogea L.) foliage grown under elevated CO(2) (550 ppm and 700 ppm) concentrations in open top chambers at Central Research Institute for Dryland Agriculture, Hyderabad, India, were examined in this study. Significantly lower leaf nitrogen, higher carbon, higher relative proportion of carbon to nitrogen and higher polyphenols content expressed in terms of tannic acid equivalents were observed in the peanut foliage grown under elevated CO(2) levels. Substantial influence of elevated CO(2) on S. litura was noticed, such as longer larval duration, higher larval weights, and increased consumption of peanut foliage by S. litura larvae under elevated CO(2) compared with ambient CO(2). Relative consumption rate was significantly higher for S. litura larva fed plants grown at 550 and 700 ppm than for larvae fed plants grown at ambient condition. Decreased efficiency of conversion of ingested food, decreased efficiency of conversion of digested food, and decreased relative growth rate of larvae was observed under elevated CO(2). The present results indicate that elevated CO(2) levels altered the quality of the peanut foliage, resulting in higher consumption, lower digestive efficiency, slower growth, and longer time to pupation (one day more than ambient).