Laboratory evaluation of azadirachtin against the oriental cockroach, Blatta orientalis L. (Dictyoptera, Blattellidae): Insecticidal activity and reproductive effects

Abstract

In this work, the toxicity of azadirachtin applied topically at various doses (300, 600, 1200, 2400, 4800 and 9000 ng/ insect) was evaluated against newly emerged adults of the oriental cockroach, Blatta orientalis L. (Dictyoptera, Blattellidae) under laboratory conditions. Results show that treated insects exhibited toxic symptoms with a dose-dependent mortality. In a second series of experiments, the compound applied topically at its LD₅₀ and LD₉₀ on newly emerged female adults was investigated on ovarian growth during the first gonadotrophic cycle (0, 2, 4 and 6 days). Azadirachtin was found to reduce the number of oocytes per paired ovaries and the size of basal oocytes. Furthermore, the compound was examined on ovarian biochemical components. Biochemical data revealed a significant reduction of ovarian contents of proteins, lipids and carbohydrates with the two tested doses. The overall results suggest an interference of the compounds with the vitellogenesis.

Key words: Azadirachtin, Blatta orientalis, toxicity, reproduction, ovary, biochemical components.