Abstract:  【Aim】 Milionia basalis is an insect pest causing serious damage to buddhist pine (Podocarpus macrophyllus) and broadleaf podocarpus (Podocarpus nagi) in southern China in recent years, and spreads rapidly, causing huge loss. This study aims to search new biocontrol agent for this pest by evaluating the pathogenicity of Metarhizium anisopliae strain MaFZ-13 against M. basalis larvae. 【Methods】 M. basalis larvae were inoculated with different concentrations (1.0×10⁵-1.0×10⁹ conidia/mL) of spore suspension of M. anisopliae strain MaFZ-13, and then the bioassay data were analyzed using time-dose-mortality (TDM) model. In the meantime, the field control efficacy against this pest was also tested by spraying the spore suspension of M. anisopliae strain MaFZ-13 at the concentration of 1.0×10⁸ conidia/mL. 【Results】 The cumulative mortality of M. basalis larvae increased with the spore concentration of M. anisopliae strain MaFZ-13 spore suspension and inoculation time. The cumulative mortality of M. basalis larvae reached 100% at 8 d after inoculation with the spore suspension at the concentration of 1.0×10⁹ conidia/mL and 10 d after inoculation with the spore suspension at the concentration of 1.0×10⁸ conidia/mL, respectively. When inoculated with the spore suspension at the concentration of 1.0×10⁷ conidia/mL, 95.6% larvae died at 15 d after inoculation. The data analysis using TDM model revealed that the constructed model fitted the data well as shown by Hosmer-Lemeshow goodness of fit test, and the values of lethal dose and lethal time of this fungal strain against M. basalis larvae were estimated with the model. The logarithm values of the estimated LC₅₀ values of M. anisopliae strain MaFZ-13 against M. basalis larvae were 7.99, 7.12, 6.46 and 5.83, respectively, at 4, 5, 6 and 7 d after inoculation. When inoculated with M. anisopliae suspension at the concentrations of 1.0×10⁷, 1.0×10⁸ and 1.0×10⁹ spores/mL, the median lethal time (LT₅₀) values of M. anisopliae strain MaFZ-13 against M. basalis larvae were 5.19, 3.99 and 2.81 d, respectively. The spore suspension of M. anisopliae strain MaFZ-13 at the concentration of 1.0×10⁸ conidia/mL caused 85.8% mortality of M. basalis larvae in the field at 9 d after spraying, with the control efficacy of 85.05%. 【Conclusion】 M. anisopliae strain MaFZ-13 has high pathogenicity and field efficacy against M. basalis larvae, with high potential application value.

Key words: Metarhizium anisopliae, Milionia basalis, bioassay, time-dose-mortality (TDM) model, field control