Avaliação do potencial do óleo essencial de Lippia origanoides kunth no controle de Meloidogyne javanica em plantas de alface

Abstract

Bioactive compounds present in essential oils (OE) of medicinal plants, have demonstrated properties that make them effective in controlling pests and diseases. Lippia origanoides Kunth is among the species with antimicrobial potential, therefore the objective of this work was to test the action of L. origanoides essential oil on M. javanica, which currently represents significant losses in world agriculture, affecting the main crops of interest economic. The objective of this study was to evaluate the in vitro and in vivo effect of O.E from L. origanoides on juvenile mortality of the second stage of M. javanica. The experimental design was completely randomized at concentrations (4, 8, 16 and 32 μL/ml) plus the control, with four replications. To verify nematicidal activity in vitro, 1000 μL of an aqueous solution containing 10% (v / v) Tween® 20, used for oil solubilization, was used, 1000 μL of M. javanica J2, containing 50 individuals. This material was taken to BOD at 28oC, and the nematode and nematicide evaluation was verified after 24 and 48 hours, respectively. For the in vivo test, theexperimental design was completely randomized at concentrations (4, 8, 16 and 32 μL L-1) plus the control, with eight replicates, after 30 days of transplanting of the seedlings, if the inoculation was carried out with 357 Individuals (eggs / juveniles J2) of M. javanica per plant, distributed in two holes two centimeters deep equidistant around the plant. 100 ml of the solution containing 10% (v / v) tween®, 990 ml of deionized water were added to the soil, the same concentrations containing eight replicates were used. In the second evaluation (48 hours) in vitro the OE was withdrawn from the solution to confirm the nematicidal activity. O.E of L. origanoides presented nematode and nematicidal activity. It was observed that immobility and mortality of juveniles from the second stage of M. javanica increased with increasing concentrations of oil, with a concentration of 32 μL L-1 responsible for causing immobility of 97% of juveniles. The nematicidal effect was confirmed by the second evaluation (48 hours), which confirmed that 84% of the nematodes immobile after 24 hours were actually dead, whereas the number of galls up to the 16 μL L-1 concentration provided a reduction of 44 and the number of galls per grams of roots, showed the same behavior with a reduction of 60% in the number of galls. The concentration 16 μL L-1 was also the most efficient reducing 52% the number of egg masses per plant and the number of galls per grams of roots. Number of egg mass per gram of roots provided a 69% reduction. The O.E. of L. origanoides shows nematicidal activity on juveniles of the second stage of M. javanica in vitro and in vivo.