SUSCEPTIBILIDAD DE Epilachna varivestis MULSANT AL ACEITE ESENCIAL DE ORÉGANO MEXICANO Y DE NEEM EN CONDICIONES DE LABORATORIO

Abstract

Toxicological bioassays were conducted on larvae of second, third and fourth instars of Epilachna varivestis, with essential oil of Mexican oregano (Lippia graveolens) from the states of Durango and Chihuahua, and neem oil (Azadirachta indica). Topical application of oregano oils were employed, applying 10 μL on the larvae dorsum, at concentrations of 0.8, 3, 5, 7 and 10 %. For Neem oil, spraying method was employed applying over each bean plant, using concentrations at 0.1, 0.5, 1, 2, 5 and 10 %. With oregano oil, mortality results were processed by Probit analysis in order to obtain the LD50 values. With oregano oil collected from Durango State, a DL50 of 38.5 μg μL-1 was obtained, whereas Chihuahua oil a DL50 of 26.15 μg μL-1, was obtained. A test of homogeneity of regression coefficients, obtaining a value of t=0.42< t=1.94 at 5 % of significance, which indicates that there was no statistical significance in toxicity values among these oils regarding their origin. In neem results, statistical significances (p<0.0001) were observed in treatments at parameters: elapsed time in each larval instar, width, length and weight of larvae, compared with the control. At 5 and 10% neem concentrations, 100% mortality was recorded at 7 DAA. Neem concentrations of 0.5, 1 and 2 % at 14 DAA causes up to 88 % mortality. Second larvae instar shown the highest mortality values.