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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.

ABSTRACT: The objective of this study was to evaluate the synergy and response homogeneity of the Spodoptera frugiperda larvae population to the Piper aduncum essential oil in combination with pyrethroid insecticides (alpha-cypermethrin, beta-cypermethrin, fenpropathrin, and gamma-cyhalothrin) compared to piperonylbutoxide (PBO) as positive control. Synergism (SF) comparisons were obtained using lethal concentration (LC50) and lethal dose (LD50) ratios of insecticides individually and in their respective synergistic combinations with essential oil and PBO. Dose/concentration-mortality slope curves were used to establish relative toxicity increase promoted by synergism. They also determined homogeneity response. Residual contact revealed significant potentiation for commercial insecticides formulated with beta-cypermethrin (SF=9.05-0.5) and fenpropathrin (SF=34.05-49.77) when combined with the P. aduncum essential oil. For topical contact, significant potentiation occurred only for alpha-cypermethrin (SF=7.55-3.68), fenpropathrin (SF=3.37-1.21), and gamma-cyhalothrin (SF=5.79-10.48) insecticides when combined with essential oil. With the exception of fenpropathrin and gamma-cyhalothrin, insecticides synergistic combinations presented homogeneous response by topical as well as residual contact at least with essential oil. The SF significance values ​​of the P. aduncum essential oil combined with alpha-cypermethrin, beta-cypermethrin, fenpropathrin, and gamma-cyhalothrin insecticides indicated potential for this oil to be used as an alternative to PBO.

O objetivo deste trabalho foi avaliar a sinergia e a homogeneidade da resposta das lagartas de Spodoptera frugiperda ao óleo essencial de Piper aduncum, em combinações com inseticidas formulados com dois princípios ativos em misturas prontas: imidacloprido/betaciflutrina, teflubenzuron/alfacipermetrina e tiametoxan/lambdacialotrina em comparação a butóxido de piperonila (PBO controle positivo). Por meio da relação das CL50 e DL50 dos inseticidas tomados isoladamente e de suas respectivas combinações sinérgicas com o óleo essencial e o PBO, foram obtidos os fatores de sinergismo (FSs) para comparação entre si. O coeficiente angular das curvas de dose/concentração-mortalidade foi utilizado para determinar a toxicidade relativa promovida pelos sinérgicos e a homogeneidade de resposta. Por contato residual, evidenciou-se significativa potencialização dos inseticidas comerciais formulados com misturas prontas de tiametoxan/lambdacialotrina (FS= 4,9 - 8,8) e teflubenzuron/alfacipermetrina (FS = 968,3 - 1.294,4), quando combinados com óleo essencial de P. aduncum. Já por contato tópico, ocorreu significativa potencialização somente com a mistura teflubenzuron/alfacipermetrina (FS= 1,6 - 7,8), quando combinada com óleo essencial. As combinações sinérgicas apresentaram homogeneidade de resposta tanto por contato tópico como residual, para pelo menos uma combinação sinérgica com o óleo essencial de P. aduncum. A significância dos valores do FS das combinações do óleo essencial de P. aduncum com os inseticidas à base de tiametoxan/lambdacialotrina e teflubenzuron/alfacipermetrina pode indicar que esse óleo essencial é uma alternativa ao PBO na promoção do efeito sinérgico.