Toxicological evaluation of three methods of applying Rhizophora mangle on Galba cubensis (Mollusca: Gastropoda: Lymnaeidae)

Abstract

The molluscicidal ecacy of Rhizophora mangle on Galba cubensis was evaluated through three bioas-says: two using aqueous extracts, one raw method extract (RME) and the other infusion method extract (IME), and direct application of powder (DAP). A completely randomized experimental design with three treatments, a control and ve replicates was used. LD50 and LD90 were determined using Probit-Log software. RME was used at 500, 400, 333 and 289 g L⁻¹ concentrations; IME at 50, 25, 12.5 and 6 g L⁻¹ ; and DAP extract at 0.540, 0.270 and 0.135 g. IME residence time and toxicity at 50 g L<sup<−1 in the substrate were also determined. We recorded 96, 80, 76, and 59 % cumulative mortalities with RME at 500, 400, 333, and 286 g L⁻¹ concentrations, respectively; LD50 was 261.4 g L⁻¹ and LD90, 442.79 g L⁻¹ . For IME, it was 100, 94, 90 and 16 % for the concentrations of 50, 25, 12.5 and 6 g L⁻¹ ; LDL50 was 8.57 g L⁻¹ and LD90, 15.83 g L⁻¹ . Mortalities with DAP extract were 70, 58, and 22 % at the 0.540, 0.270 and 0.135 g concentrations respectively, none of which reached LD90 and only the 0.540 g concentration reached LD50. IME residence and toxicity at 50 g L⁻¹ decrease signicantly after eight hours.