D-limonene combined with Bacillus thuringiensis against Spodotera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae)

Abstract

Focusing on alternatives for better control of S. frugiperda, research has proven the efficiency of using natural compounds to reduce the emergence of resistance. Consequently, the combination of different modes of action of natural insecticide, capable of enhancing the action of each molecule, promoting a barrier to the pest resistance. So, this work evaluated the toxicity of d-limonene associated with entomopathogenic microorganisms against S. frugiperda. A population of caterpillars was assembled in the laboratory to conduct in vitro toxicity assays. A range of insecticide dilutions was carried out and then applied to larvae, with the aim of obtaining the dose-response curve. After determining the lethality of each product and aiming to determine the synergistic potential between them, several binary combinations were established. D-limonene essential oil promoted high mortality of caterpillar at very low concentrations, and the subspecies of bacilli used ensured high caterpillar mortality. However, the strain of B. bassiana used promoted caterpillar mortality only at a very high dose. B. bassiana + d-limonene presents synergistic properties with very high toxicity to S. frugiperda. B. thuringiensis + d-limonene, although resulting in toxicity for larvae, does not appear to be synergistic.