Effect of essential oils and selected components on Heterorhabditis amazonensis Andaló et al. strain HC1

The effect of four essential oils and eleven selected components on the infective juveniles (IJ) of the entomopathogenic nematode Heterorhabditis amazonensis Andaló et al. strain HC1 was studied under laboratory conditions. Susceptibility of this strain to seven organic solvents and surfactants was determined. The lethal and sublethal toxic effects on IJ exposed directly to the essential oils and components were evaluated in 24 well plates for 24 h. Data of lethal toxic effects were subjected to ANOVA and the means compared by Duncan´s multirange test at 0,05 %, whereas data of sublethal toxic effects were analyzed by the multiple comparison of proportions (Wald´s Method, confidence level of 0,05). Toxicity of Triton X-100 at 0,5 % on H. amazonensis strain HC1 was low and could be used in bioassays of chemical product compatibility with this nematode strain. The essential oils of Melaleuca quinquenervia (Cav) S.T. Blake and Citrus sinensis (L.) Osbeck caused no significant lethal toxic effect on IJ of H. amazonensis (strain HC1), while those of Piper aduncum subsp. ossanum (C. DC.) Saralegui and Piper auritum Kunth produced moderate mortality. No sublethal effects were caused by these four oils on the infectivity of IJ of H. amazonensis strain HC1. The essential oil components camphene, p-cymene and piperitone did not affect IJ of H. amazonensis strain HC1; 1,8-cineole, limonene, camphor, and methyl chavicol showed moderate toxicity, and carvacrol, eugenol, linalool, and thymol were highly toxic. According to the parameters evaluated, the essential oils from M. quinquenervia and C. sinensis and the components camphene, p-cymene, and piperitone were compatible with H. amazonensis strain HC1.