Synergistic potential of dillapiole-rich essential oil with synthetic pyrethroid insecticides against fall armyworm/Potencial sinergico do oleo essencial rico em dilapiol para inseticidas piretroides sinteticos frente a lagarta-do-cartucho

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, betacypermethrin, fenpropathrin, and gamma-cyhalothrin) compared to piperonylbutoxide (PBO) as positive control. Synergism (SF) comparisons were obtained using lethal concentration (LC50) and lethal dose (LD0 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=3.371.21), 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, betacypermethrin, fenpropathrin, and gamma-cyhalothrin insecticides indicated potential for this oil to be used as an alternative to PBO. Key words: alpha-cypermethrin, beta-cypermethrin, fenpropathrin, gamma-cyhalothrin, insecticide resistance. O objetivo deste trabalho foi avaliar a sinergia e homogeneidade de resposta de lagartas de Spodoptera frugiperda ao oleo essencial de Piper aduncum, em combinacoes com inseticidas do grupo dos piretroides: alfa-Cipermetrina, beta-Cipermetrina, Fenpropatrina e gama-Cialotrina, em comparacao ao butoxido de piperonila (PBO controle positivo). Por meio da relacao das CL50 e DL50 dos inseticidas tomados isoladamente e de suas respectivas combinacoes sinergicas com o oleo essencial e o PBO, foram obtidos os fatores de sinergismo (FS) para comparacao entre si. O coeficiente angular das curvas de dose/concentracao-mortalidade foi utilizado no estabelecimento do aumento de toxicidade relativa, promovida pelos sinergicos e determinacao da homogeneidade de resposta. Por contato residual, evidenciou-se significativa potencializacao