Essential oils from Piper aduncum L., Piper hispidinervum C. DC. (Piperaceae) and Tanaecium nocturnum (Barb. Rodr.) Bur.& K. Shum (Bignoniaceae) were tested against Tenebrio molitor L., 1758 larvaes. Filter paper with different amounts of oils were employed for contact toxicity effects study. For topical effect study, aliquots of 5 mL of oils at different concentrations were applied on larvaes of the fifth instar. Mortality rate was used to evaluate the assays. All essential oils possessed insecticidal effect to T. molitor, but the responses varied according to oil concentration and method of exposure. The toxicities ofessential oils to T. molitor were elevated, with LC50 of 0.045, 0.033 and 1.515 mL of the oil/cm² for contact (filter-paper) applications of the P. hispidinervum,P. aduncum and T. nocturnum oil, respectively. For topical application the values of the LD50 were: 0.000025, 0.009 and 0.000015 mL of the oil /mg of the insect, for P. hispidinervum,P. aduncum and T. nocturnum oil, respectively. The most promising results for the use of such oils as insecticide were obtained using concentrations above 3,0% (v v-1) for P. hispidinervum and 2,5% (v v-1) for P. aduncum and T. nocturnum essential oils.
Long piper; dillapiol; safrole; mandelonitrile; plant insecticide
