Impact of elevated CO2 on lepidopteron insect pests of Castor

Abstract

The growth, development and consumption of four successive generations of castor semilooper, Achaea janata 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 CRIDA, 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 grown under elevated carbon dioxide levels. Significant influence of elevated carbon dioxide on life history parameters of A. janata over four generations was noticed. Longer larval duration, differential pupal weights and increased larval survival rates of A. janata in successive four generations were observed under elevated carbon dioxide than ambient. Reduced fecundity was observed over generations under each elevated carbon dioxide level. The consumption per larva of A. janata fed on castor foliage grown under elevated carbon dioxide increased from first to fourth generation. Potential population increase index for successive generations was found lower in both elevated carbon dioxide concentrations than in case of ambient. The present findings indicate that elevated carbon dioxide levels significantly altered the quality of the castor foliage resulting in higher consumption by larvae, better assimilation higher values of relative consumption rate and approximate digestibility, slow growth (lower relative growth rate) and took longer time (two days more than ambient) to pupation to produce in less fecund adults over generations.