Synergistic effect of a fungicide containing polyoxin B with insect growth regulators (IGRs) in the killing of common cutworm, Spodoptera litura (Lepidoptera: Noctuidae)

Abstract

Polyoxin AL water-soluble powder (Polyoxin AL), a fungicide that inhibits chitin synthase, showed a synergistic effect with benzoylphenyl urea insect growth regulators (BPU-IGRs) in killing Spodoptera litura larvae. First, eight different commercially available insecticides were examined for a synergistic effect with Polyoxin AL in killing S. litura. Only Cascade, one of the BPU-IGRs, showed a synergistic effect. Next, eight BPU chemicals (six BPU-IGRs including Cascade and two reagents) were used. All eight chemicals showed a synergistic effect except for Dimilin. Finally, six fungicides, including Polyoxin AL, were examined for a synergistic effect with Cascade. Only Polyoxin AL showed a synergistic effect. These results suggest that the synergistic effect was specific for the combination of BPU chemicals and Polyoxin AL.