Efficacy of Some Plant Extracts on Lucilia Sericata (Meigen) (Diptera: Calliphoridae)

Zinc sulfate is a promising insecticide qualifying for disrupting the growth, development and reproduction of treated insect pests. This study was carried out to evaluate the toxicology of Zinc sulfate, its ability as an insect growth inhibitor and as a stimulant of the oxidative stress of the Spodoptera littoralis fourth instar larvae and the histological disruption it causes in the reproductive organs. The five zinc sulfate concentrations (1-2-3-4-5%) used in the toxicity experiment were all effective against the fourth instar larvae of Spodoptera littoralis with mortality percentage ranging from 53 to 95% 7 days post-treatment and the LC50 value is 0.9%. Zinc sulfate proved its growth inhibition ability whereas, a significant difference in the larval weight between the treated and untreated ones was noticed and the percentage of the weight reduction reached 92% of the larvae treated with the highest concentration used (5%). Vitamin C and the antioxidant enzymes (GST, peroxidase and phenoloxidase) were determined after 5 days and it was noticed that there is a decrease in Vitamin C and phenoloxidase levels (50±3.60) and (23.66±1.25) compared to that of the control (59.66±6.11) and (33.1±1.92) and great elevation in the level of both GST and Peroxidase (1336.67±56.86 and 37±2.68) compared to control one (933.3±32.53 and 28.67±1.42) respectively. The histological examinations of male and female reproductive organs (testis and ovary) of adult Spodoptera littoralis treated with the zinc sulfate LC50 confirmed that the Zinc sulphate induced marked histopathological alterations when compared with the control group. In ovaries, necrosis, vaculation and degeneration were recorded. In testes, vaculation and atrophied follicles were observed.