TOXIC EFFECT OF CRUDE ALKALOID EXTRACT OF CITRULLUS COLLOCYNTHIS AGAINST CULEX PIPIENS (DIPTERA: CULICIDAE)Maallh T. Al-Husseini, H.M. Al-Rubae and H.R. Al-MousawiAbstract The present study was carried out to investigate the toxic effect of crude alkaloid extract of Citrullus colocynthis on the mortality rates of immature larval instars of Culex pipiens mosquito (Diptera: Culicidae). Results of the present study showed that crude alkaloid extract was more toxic to the first and second instars larvae and mortality rates were reached at concentration 20 mg/ml to (87.2 and 79.6 %) respectively compared to (4.6 and 3.8 %) respectively at control treatments. Whereas the 3rd and 4th instars larvae were less toxic and mortality rates were reached at concentration 20 mg/ml to (66.4 and 50.2 %) respectively compared to (1.4 and 1.2 %) respectively at control treatments. Egg mortality rates were also increased at higher concentrations 20 mg/ml to reach 50.2 % compared to 9.6 % at control treatments. Pupae stages were more resistant at higher concentrations 20 mg/ml reached to 41.7 % compared to 6.4 % at control treatments. The present study also revealed that crude alkaloid extract of C. collocynthis negatively impact on hatchability, immature stages development period and female productivity. Moreover the present study showed that cumulative mortalities rates were increased as the concentrations raised resulting in that crude alkaloid extract of C. collocynthis was more toxic against of immature stages of Culex pipiens mosquito. |