Abstract

The molluscicidal activities of aqueous and ethanolic extracts of leaves of Chromolaena odorata were investigated on adult, one week old juveniles and 3 to 4 days old egg-masses of Biomphalaria pfeifferi. Ten adults each were exposed to a serial dilution of 40, 80, 160, 240, 320, 400, and 480 ppm distilled water extracts and 20, 40, 80, 160, 240 and 320 ppm ethanolic extracts of leaves of C. odorata. Twenty juveniles of uniform size each were exposed to 8, 20, 28, 40, 80, 120, and 160 ppm of aqueous and ethanolic extracts of the same plant. The adults and juveniles were exposed to the extracts for 24 h. Thirty eggs each were exposed to 8, 20, 28, 40, 60, 80, and 100 ppm of aqueous and ethanolic extracts for a period of 48 h. The experiments were repeated twice. LC₅₀ obtained with aqueous extract against eggs, juveniles and adults were 65.75, 75.59 and 217.57 ppm, respectively while these values were 44.03, 44.68 and 88.04 ppm, respectively for ethanolic extract. The LC₉₀ obtained with aqueous extract against eggs, juveniles and adults were 139.54, 249.54 and 288.96 ppm, respectively. These values were 119.03, 123.50 and 245.61 ppm, respectively for ethanolic extract. The plant extracts caused significant (P<0.05) mortality rates in the different stages of B. pfeifferi. C. odorata seem to be a promising plant molluscicide candidate and deserve further studies in order to identify and characterize its molluscicidal components.

Key words: Schistosomiasis, Chromolaena odorata, Biomphalaria pfeifferi, molluscicidal activities, LC₅₀, LC₉₀.