Combining the essential oil of Piper aduncum L. with commercial insecticides

The use of synergists is important to minimize the amount of chemical insecticide required for insect control. Their use may contribute to reducing environmental contamination and preserving beneficial insects. The aim of this study was to evaluate the synergy and uniformity of the response of Spodoptera frugiperda (Noctuidae) larvae to doses of an essential oil of an Amazon chemotype, Piper aduncum (Piperaceae), when combinationed with the following commercial insecticides: cypermethrin, zeta-cypermethrin, permethrin and esfenvarelate, compared to piperonyl butoxide (PBO). Through the relationship between CL50 and DL50 of insecticides taken separately and their synergistic combinations with the essential oil and PBO, synergism factors (SF) were obtained for comparison with each other. With residual contact, there was a significant enhancement of commercial insecticides formulated with cypermethrin (SF = 73.03), zeta-cypermethrin (SF = 16.51) and permethrin (SF = 8.46-17.22), when combined with the P. aduncum essential oil; in turn, with topical application, there was only an observed significant enhancement for zeta-cypermethrin (SF = 0.40-4.26), permethrin (SF = 2.10-4.79) and esfenvarelate (SF = 3.80) insecticides when combined with the essential oil. With the exception of esfenvarelate, the other synergistic combinations showed homogeneous responses for topical application and residual contact for at least one synergistic combination with P. aduncum essential oil. The significance of the SF values from combining P. aduncum essential oil with cypermethrin, zeta-cypermethrin, permethrin and esfenvarelate insecticides may indicate that this essential oil is an alternative option to PBO.