Beauveria pseudobassiana: A good candidate for controlling Diprion pini L. (Hymenoptera: Diprionidae)

Abstract

The common pine sawfly, Diprion pini (Linnaeus, 1758) (Hymenoptera: Diprionidae), is a well-known defoliating pest of various pine forests almost all over the world, including Europe. It can cause damage to many pine species but usually opts for Pinus sylvestris Linnaeus and P. nigra subsp. laricio (Poiret) Maire. The prohibition of the use of chemical insecticides in forests (at least for Türkiye) has led to the fact that other control methods have come to the fore in the control of this pest. In this respect, biological control agents, which are eco-friendly and can persist in the field over time, providing long-term control for plant protection, have an important potential in the control of D. pini. Therefore, in this study, entomopathogenic fungi were isolated from pine forest soils and identified by gene sequencing and phylogenetic analysis. Ten isolates (DP-37, DP-38, DP-45, DP-46, DP-49, DP-53, DP-54, DP-57, DP-58 and DP-63) were identified as Beauveria pseudobassiana, four isolates (DP-35, DP-41, DP-52, and DP-61) were identified as B. bassiana, and only one isolate was identified as Metarhizium robertsii (DP-15). All isolates were tested against the larvae of the pest under laboratory conditions, and the highest mortality and mycosis values (96.6% and 63.3%, respectively) were obtained from B. pseudobassiana DP-57. This isolate was also tested against the pest under outdoor conditions using different conidial concentrations. Based on probit analysis, the LC₅₀ and LC₉₀ values were estimated to be 1.309 × 10⁷ and 1.21 × 10¹⁰ conidia/ml, respectively. The results showed that B. pseudobassiana DP-57 could be a good candidate in the biological control of D. pini.