New data on the Metarhizium pemphigi pathogenicity against economically and ecologically important insect species in laboratory conditions

This paper presents a comparative study on the pathogenicity of Metarhizium pemphigi against different insect pests (Ips acuminatus, Ips sexdentatus, Taphrorychus bicolor, Oulema melanopus, Oxycarenus lavaterae, and Corythucha arcuata) under laboratory conditions. The mortality rates were determined for different conidia concentrations. Overall, the average mortality rate for all insect species tested was 21.05 ±7.41% after treatment with 2 × 10⁵ conidia/ml and 98.79 ±1.21% after treatment with 2 × 10⁹ conidia/ml. Mortality rates varied significantly among insect species, especially at lower conidia concentrations. Depending on the tested insect species, the mean values of LC₅₀ and LC₉₀ varied from 0.29 to 77.80 × 106 conidia/ml and from 10.14 to 417.10 × 106 conidia/ml, respectively, with probit regression slopes ranging from 0.74 to 0.90. The tested strain of M. pemphigi was the most virulent to T. bicolor and also showed high efficacy against I. acuminatus, C. arcuata, and O. melanopus. Conversely, I. sexdentatus displayed the lowest susceptibility to this fungus. Estimated mean survival times of the insects, after treatment with 2 × 10⁶ conidia/ml, ranged from 5.32 to 9.05 days, depending on the insect species. The shortest survival time was estimated for T. bicolor, and the longest for O. lavaterae. The study highlights the potential of M. pemphigi for biocontrol of the tested insect species and calls for further research to explore its full capabilities and potential applications.