Effect of Vermicompost on Life History of Hippodamia variegata Preying on Aphis gossypii Glover
Keywords:Organic fertilizer, population growth, Hippodamia variegata.
The variegated ladybird beetle,Â Hippodamia variegataÂ (Goeze), with worldwide distribution is among the most successful predators of aphids. In this study, the life history ofÂ H.Â variegataÂ feeding onÂ Aphis gossypiiÂ Glover as prey was evaluated on cucumber plants treated with different vermicompost concentrations (0, 15 and 30%) in a growth chamber at 25 Â± 2Â° C, 60 Â± 10% RH, and 16:8 (L: D) h. The results showed that demographic parameters ofÂ H. variegataÂ were affected by vermicompost treatments. Duration of total developmental time of larvae and pupal period ofÂ H.Â variegataÂ on the tested vermicompost concentrations were significantly different. No significant differences were found for the adult longevity, life span, fecundity, and oviposition period ofÂ H.Â variegataÂ 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 (Î»), net reproductive rate (R0) and doubling time (DT) ofÂ H.Â variegataÂ among different vermicompost treatments were significant; The values ofÂ rmÂ andÂ R0Â increased as the percentage of vermicompost increased from 0 to 30%. It seems that some population growth parameters ofÂ H. variegataÂ 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 ofÂ H. variegataÂ which would make it as a suitable predator ofÂ A. gossypiiÂ in vermicompost-treated plants.
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