Synergistic activity of several acids in binary mixtures with synthetic insecticides on Spodoptera littoralis (Boisduval)

Abstract

The activity of binary mixtures of some inorganic acids (IAs) and organic acids (OAs) with certain recommended insecticides was evaluated against the 4th-instar larvae of Spodoptera littoralis in laboratory. Mixing organophosphate, pyrethroid and carbamate compounds with IAs and OAs have shown some useful synergistic effect. The joint effect of chlorpyrifos-methyl and esfenvalerate with IAs combinations showed a slight synergism by two IAs after 48h. However, the combination with methomyl resulted in highly synergistic activity after 48h, especially when methomyl was combined with phosphomolybdic acid. On the other hand, the combination of chlorpyrifos-methyl and esfenvalerate with ortho-phosphoric acid and phosphomolybdic acids resulted in antagonistic activity. Regarding the combinations of chlorpyrifos-methyl with OAs, data revealed that 9 of 16 showed synergism while the rest of cases showed antagonism after 48h. The combinations of esfenvalerate with OAs showed synergism in 13 of 16 binary mixtures, and antagonism in 3 cases after 48h. Combinations of methomyl and OAs, was found that both acetic and linolenic acids exhibited high synergistic activity followed by hexanoic and oleic acids. In adittion, antagonistic effect was noticed in binary mixtures of 4 OAs after 48h.