Entomopathogenic potential of Purpureocillium lilacinum against the model insect Galleria mellonella (Lepidoptera: Pyralidae)

Abstract

Pathogenicity of the entomopathogenic fungus Purpureocillium lilacinum against Galleria mellonella larvae was studied using two application methods, immersion and injection. G. mellonella last instar larvae were immersed and injected with fungal suspensions of different conidial concentrations (1 × 103, 1 × 104, 1 × 105, 1 × 106, 1 × 107 and 1 × 108 conidia mL–1) and mortality was recorded daily. P. lilacinum showed pathogenicity at the different concentrations by both methods. P. lilacinum was highly infectious for G. mellonella causing 100% larval mortality within 7 days post-immersion with 1 × 108 concentrations. The median lethal time (LT50) was 1.83 days. Using the injection method, 1 × 108, 1 × 107, 1 × 106 and 1 × 105 concentrations caused 100% larval mortality within 1, 2, 3 and 4 days after injection respectively. The median lethal time (LT50) was 1, 1.47, 1.96, aand 2.05 days, respectively. For both methods (immersion and injection) the lethal concentration of P. lilacinum that caused 50% larval mortality (LC50) was 3.1 × 10 4 and 4.7 × 103 conidia mL–1, respectively. Both methods were effective on larvae, but the injection method was more effective than immersion method at 4.7 × 103 conidia mL–1 causing 50% larval mortality. For immersion and injection methods, the median lethal times (LT50) at the concentrations of 1.0 × 108 conidia mL–1 were 1.83 and 1 days, respectively. The pathogenicity results obtained from this isolate using the model insect G. mellonella showed that P. lilacinum can be used as a potential biopesticidal agent against lepidopteran pests.