Morphological and molecular characterization of Purpureocillium lilacinum along with its biopesticidal effect against fall armyworm (Spodoptera frugiperda) in Southern Taiwan

Abstract Background Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), a key agricultural pest, impacts a broad spectrum of crop species, such as cotton, maize, rice, sorghum, and a range of vegetables. Chemical pesticides and transgenic maize are commonly used to protect crops against this major pest. However, biological control offers a safer and more sustainable solution for long-term FAW management. Entomopathogenic fungi (EPF), a substitute for synthetic insecticides, have been proven to be an effective biocontrol agent for managing pest populations. The present study objective is to isolate and identify the EPF, Purpureocillium lilacinum from soil using morphological and molecular techniques and evaluate its pathogenicity against FAW eggs and various larval stages under different spore concentrations. Results The micro-morphological characteristics fluctuated in growth behavior, appearance, and color under diverse growth media and temperatures. Molecular analysis, which involved constructing a phylogenetic tree from ITS and TEF gene regions, confirmed that PT-02 was P. lilacinum. The pathogenicity of the fungus was tested on FAW eggs, neonates, and larvae at multiple concentrations (1 × 108, 1 × 107, and 1 × 106 spores/ml), resulting in variation mortality. The egg mortality rate at 1 × 108, 1 × 107, and 1 × 106 spores/ml was 98, 98 and 96%, respectively. The neonate mortality rate was 100%, while first and second instars larvae mortality ranged from 10–36% across three concentrations, seven days after treatment (DAT). The median lethal concentration (LC50) values of P. lilacinum PT-02 against FAW eggs, first and second instars, were 3.02 × 107, 1.38 × 108, and 2.56 × 108 spore/ml, respectively. Conclusions The findings revealed that the native strain of P. lilacinum exhibited strong virulence against FAW, suggesting its potential use as an effective biocontrol agent for managing field pest populations.