Susceptibilidad de Plutella xylostella (L.) a tres extractos acuosos vegetales, bajo condiciones de laboratorio.

Abstract

The objective of this research was to evaluate the toxicity of three plant extracts on second instar larvae of Plutella xylostella (L.), under laboratory conditions. For the treatments, leaf extracts were used at concentrations of 100% (100,000mg/l), 75% (75,000mg/l), 50% (50,000mg/l) and 25% (25,000mg/l) and a control which had no concentration. Leaves were taken from hemlock, cow's tongue and cariaquito plants. The experimental design was completely randomized, for the three extracts; each one with five concentrations and each concentration with five replicates and each replicate with five P. xylostella larvae. To obtain the mortality of larvae or the emergence of moth adults, observations were made every 12 hours during the course of 12 days. The data were analyzed using SPSS software and Tukey tests to determine significant differences between treatments. To calculate the LC50, the concentrations were transformed to log10 and the mortalities to Probit, and with the accumulated mortalities, the TL50 was found by Regression Analysis. It was obtained that the concentration of 100,000mg/l of aqueous extracts of hemlock leaves caused the death of 100% of larvae with significant differences; the concentration of 100,000mg/l of cow tongue extracts caused 84% mortality; while the concentration of 100,000mg/l of cariaquito leaf extracts caused 76% mortality with significant differences with the other concentrations. The LC50 determined were for hemlock 28,183mg/l, for cow tongue 7,585mg/l and 20,892mg/l for the aqueous cariaquito extracts, to kill 50% of the larval population of the bioassay. The TL50 for hemlock extracts at its concentration of 100,000mg/l was 98 hours, for cow tongue extracts it was 73 hours and cariaquito extracts caused the death of 50% of the larvae at 305 hours.