Effect of Three Plants Extracts on Some Bacterial Strains and Culex pipiens L. Stages

Use of natural antimicrobial and insecticidal agents represents a safe vector control. Plant extract activity of Calotropis procera, Acacia nilotica and Cassia senna was investigated against some food borne pathogens (Escherichia coli, Salmonella typhimurium, Staphylococcus aureus sub sp. aureus and Bacillus cereus), food spoilage microorganisms (Bacillus cereus and Bacillus stearothermophilus) and towards larval mortality and development of Culex pipiens L. Antimicrobial activity of cold and hot aqueous extracts was studied. It was found that hot extract of C. senna has the strongest inhibition effect on Staphylococcus aureus sub sp. aureus, Salmonella typhimurium and Bacillus stearothermophilus. Acacia nilotica showed only complete inhibition of Staphylococcus aureus sub sp. aureus, Salmonella typhimurium. It was found that hot extracts of Cassia senna and Acacia nilotica have bactericidal effect on Staphylococcus aureus sub sp. aureus and Salmonella typhimurium. Acetonic plant extracts exhibited variable biological activity. The greatest was observed for A. nilotica which showed acute (2 days) and chronic (10 days) LC 50s of 212.1 and 144.2 ppm, respectively. Larval mortality up to 93.33% and reduction of egg hatchability was observed with A. nilotica extract. At every concentration level all plant extracts caused significantly high hindrance to subsequent larval development and reduced both pupation and adult emergence. Drastic retardation of development was shown by A. nilotica extracts when reared in very low concentration (100 ppm). However, C. senna and C. procera were more effective at higher concentrations. Application of such plant extracts to mosquito breeding sites may have great practical importance in relation to non-synthetic chemical control of these serious disease vectors.