Ação inseticida in vitro do óleo essencial de Lippia gracilis Schauer sobre Damalinia (Bovicola) ovis Schrank (1781)

Abstract

The objective of this work is to evaluate the in vitro insecticidal efficacy of the essential oil of Lippia gracilis against Damalinia (Bovicola) ovis. The specimens (n ​​= 900) of D. (Bovicola) ovis were collected from naturally infested sheep, randomly distributed in groups, and subjected to different treatments: (G1) 1,000 to 15.6 mg/ml essential oil of Lippia gracilis; (G2) 3% Tween 80 (negative control), and: (G3) Amitraz 1.25 g/mL (positive control). 4 replicates (25 lice per replica) were performed for each treatment. Louse viability was assessed at 1, 3, 6, 24, 48 and 72 h. The data were expressed as mean efficacy ± standard deviation (SPSS version 23.0) and statistical differences in the experimental groups were obtained by Kruskal-Wallis and Friedman. Probit regression was performed to obtain the IC₅₀ and CI₉₀, with a significance level of p <0.05. The essential oil of L. gracilis at concentrations of 100 to 62.5 mg/mL showed 100% efficacy, 1 h post-exposure. The IC₅₀ and CI₉₀ values ​​were 18.1 mg/mL and 44.9 mg/mL, respectively. Thus, we conclude that L. gracilis essential oil is effective on D. (Bovicola) ovis.