Pathogenicity of two fungal pathogens on larvae of the elm leaf beetle, Xanthogaleruca luteola Muller (Coleoptera: Chrysomelidae)

Background The elm leaf beetle (ELB), Xanthogaleruca luteola Muller (Coleoptera: Chrysomelidae), is one of the most important insect pests that cause damage and physiological stress for the trees. In the present research, pathogenicity of both entomopathogenic fungi (EPF), Beauveria bassiana and Metarhizium anisopliae on the 1st, 2nd, and 3rd instar larval of ELB at the concentrations of 105, 106, 107, and 108 conidia per ml, using immersion and spray methods and were evaluated. Results The results showed that LC50 of B. bassiana in immersion and spray methods were 3.88 × 102 and 7.52 × 102 conidia/ml, while LC50 of M. anisopliae in mentioned methods were 7.05 × 102 and 11.85 × 102 conidia/ml, respectively. The highest mortality rate in both EPF was observed in the 1st instar larvae that were significantly different than the control treatment. Moreover, the highest and lowest mortality in both EPF, using immersion and spray methods, were observed at the concentrations of 108 and 105 conidia/ml, respectively. Therefore, susceptibility of 1st and 2nd larval instars was more than 1st instar larvae. Based on the findings of the present study, there was no mortality during the first 24 h, while after 2 days, the mortality was recorded and increased over time in case of both pathogens. Accordingly, B. bassiana and M. anisopliae were pathogenic on larvae of ELB. Conclusions The outputs of the study demonstrated that applications of these eco-friendly fungal pathogens with other non-chemical methods are recommended. Of course, under natural conditions, their efficiency may change; thus, more comprehensive studies are necessary.