Phthorimaea operculella is a globally distributed pest of solanaceous crops and represents one of the most critical constraints on potato production worldwide. The overuse of chemical insecticides has led to widespread resistance in pest populations, making entomopathogenic fungi a promising alternative strategy for sustainable agricultural pest management. In this study, a fungal strain designated ML-2 was isolated from naturally infected P. operculella larvae collected from a potato field in Yunnan province, China. Through morphological characteristics and ITS sequence analysis, strain ML-2 was identified as M. robertsii. The growth rate and sporulation yield on PDA and SDAY media were assessed, the virulence of ML-2 against eggs, larvae, and pupae of P. operculella were determined using the dipping method, and the data were analyzed via the time-concentration-mortality (TCM) model. The results showed that there were no significant differences in the growth rate of strain ML-2 on the two culture media (p > 0.05), whereas the sporulation yield on PDA medium was significantly higher than that on SDAY medium (p < 0.01). The highest corrected cumulative mortality rates for P. operculella larvae and pupae were 94.50% and 83.07% on day 7 after inoculation, respectively, while the highest cumulative mortality rate for eggs was relatively low at only 20.28%. Additionally, at a concentration of 1 × 108 spores/mL, the LT50 values of strain ML-2 against P. operculella larvae and pupae were 2.34 days and 2.72 days, respectively. On day 7 post-inoculation, the LC50 values for larvae and pupae were 3.24 × 107 conidia/mL and 9.64 × 105 conidia/mL, respectively. In conclusion, M. robertsii ML-2 exhibits high potential as a candidate biopesticide and can be used in the sustainable integrated management of P. operculella.
Zhang et al. (2026) studied this question.