Effect of Vermicompost on Life History of Hippodamia variegata Preying on Aphis gossypii Glover

Abstract

The variegated ladybird beetle, Hippodamia variegata (Goeze), with worldwide distribution is among the most successful predators of aphids. In this study, the life history of H. variegata feeding on Aphis gossypii Glover as prey was evaluated on cucumber plants treated with different vermicompost concentrations (0, 15 and 30%) in a growth chamber at 25 ± 2° C, 60 ± 10% RH, and 16:8 (L: D) h. The results showed that demographic parameters of H. variegata were affected by vermicompost treatments. Duration of total developmental time of larvae and pupal period of H. variegata on the tested vermicompost concentrations were significantly different. No significant differences were found for the adult longevity, life span, fecundity, and oviposition period of H. variegata when fed on aphids reared on vermicompost-treated cucumber plants. Based on the results, the differences of intrinsic rate of natural increase (rm), finite rate of increase (λ), net reproductive rate (R0) and doubling time (DT) of H. variegata among different vermicompost treatments were significant; The values of rm and R0 increased as the percentage of vermicompost increased from 0 to 30%. It seems that some population growth parameters of H. variegata were positively affected by high rates of vermicompost. Our results showed that the addition of vermicompost to the growing medium of cucumber plants could positively affect some of the demographic parameters of H. variegata which would make it as a suitable predator of A. gossypii in vermicompost-treated plants.