Vol. 8, Issue 4, Part A (2021)

Author(s): Atallah F Mekhlif and Muhammad J Muhammad

Abstract: The bio-insecticidal activity of the medicinal plants: Physalis angulate, Peganum harmala, Tecrium polium and Thymus vulgaris had been tested on fourth instar larvae of Culex pipiens molestus according to WHO protocol. LC₅₀ and LC₉₀ had been estimated after 24 and 48 hrs. exposure. As ascending values: LC₅₀ at 24 hrs. were 1.8, 26.0, 34.0, and 45.0 ppm and at 48 hrs. were 1,5, 11.0, 23.0 and 38.5 ppm for P. angulate, P. harmala, T. polium and T. vulgaris respectively. The residual action determination for the plant extracts and positive control (Igon® insecticide) was began at first - day time with concentration caused 100% mortality, these concentrations of the extracts were 5, 50, 60 and 100 ppm for P. angulate, P. harmala, T. polium and T. vulgaris respectively, the extracts activity decreased and their mortalities had been declined to about 50% (except P. harmala extract) after 9 - 12 days of application, all the applied extracts had diminished their toxicity at 15^{th -} day observation.