Control Efficacy of Entomopathogenic Fungus Purpureocillium lilacinum against Chili Thrips (Scirtothrips dorsalis) on Chili Plant

Abstract

In a laboratory assay, it was shown that <i>B. bassiana</i> BCC48145, BCC2660, and <i>P. lilacinum</i> TBRC10638 were the three strains that exhibited the highest insecticidal activity against chili thrips, causing 92.5% and 91.86% and 92.3% corrected mortality, respectively. The fungi <i>B. bassiana</i> BCC48145 and <i>P. lilacinum</i> TBRC10638 were selected for greenhouse spraying. Cytotoxicity test of the extracts from both fungi evaluated against 4 animal cell lines: KB; human oral cavity carcinoma, MCF7; human breast adenocarcinoma, NCI-H187; human small cell lung carcinoma and GFP-expressing Vero cells, showed none-cytotoxic to all cell lines. An efficacy validation in the greenhouse showed that <i>P. lilacinum</i> TBRC 10638 was more effective than <i>B. bassiana</i> BCC48145 and could control the thrips up to 80% when using the fungus at 10⁸ spores/mL. The LC₅₀ values of <i>P. lilacinum</i> TBRC 10638 against chili thrips based on total thrips count from two experiments were 1.42 × 10⁸ and 1.12 × 10⁷ spores/mL when the fungal spores were sprayed once a week. The optimal concentration of <i>P. lilacinum</i> TBRC 10638 spores for effective control of chili thrips was determined at 1.41 × 10⁹ spores/mL. The average efficacy of <i>P. lilacinum</i> TBRC 10638 for thrips control from 3 field trials was 30.08%, 14.39%, and 29.92%. This result was not significantly different from that of the chemical insecticide treatment group, which showed efficacy at 19.27%, 14.92%, and 19.97%. Furthermore, there was no difference in productivity among the different treatment groups. Our results demonstrated that <i>P. lilacinum</i> TBRC 10638 is a promising biocontrol agent that could be used as an alternative to chemical insecticide for controlling chili thrips.