In vitro effect of extracellular enzymes and conidia from Beauveria bassiana on Spodoptera frugiperda pupae

Abstract

Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) has caused significant economic losses and food security challenges. Furthermore, its management may result in the overuse of synthetic pesticides. Therefore, this study aimed to assess the in vitro efficacy of extracellular enzymes and B. bassiana conidia against S. frugiperda pupae. The enzymes were produced through solid-state fermentation (rice with whey) using a B. bassiana isolate (IP 361). After production, the enzymes were concentrated by precipitation, and the activity was measured. For the in vitro virulence assay on S. frugiperda pupae, the following groups were established: G1: negative control (distilled water); G2—positive control (chlorpyrifos insecticide); T1—conidia (107 conidia mL−1); T2—active precipitated extract; T3—denatured precipitated extract; T4—conidia (107 conidia mL−1) + active precipitated extract. Percent mortality was recorded at (10 days) post treatment. After precipitation, the specific activity for protease was 180 U mg‑1 and chitinase was 0.207 U mg‑1. Percentage mortality of S. frugiperda pupae for the active extract days post treatment was 100%, compared to the control and denatured treatments (p < 0.01). There was no significant difference (p > 0.01) between the active extract and the positive control. Suspensions of conidia with active extract and conidia alone caused mortalities of 73% (p > 0.01) and 63% (p > 0.01). The results indicate that the in vitro use of these B. bassiana enzymes can have the same lethal effect as the insecticide chlorpyrifos. Therefore, these enzymes show great potential as a sustainable alternative control of S. frugiperda.