Abstract

The willow leaf beetle, Plagiodera versicolora (Laicharting, 1781), is one of the most destructive pests of manySalix and Populus species worldwide. A total of 12 entomopathogenic fungi including Beauveria bassiana(Bals.) Vuill., B. cf. bassiana, Metarhizium anisopliae (Metch) Sorok, and Isaria fumosorosea (Wize) (formerlyPaecilomyces fumosoroseus) were tested against the larvae of this pest under laboratory conditions in order to find any possible fungal biocontrol agent against it. A conidial concentration of 1 × 10⁷ conidia ml^-1 for each isolate was applied to third instar larvae of the pest. Among tested fungal isolates, the highest mortality was obtained as 100% from B. bassiana KTU-57 within 14 days after inoculation (p < 0.05). This isolate also caused the highest mycosis value (83%) (p < 0.05). It was selected for dose-response test according to the screening test, and lethal concentration at 50% (LC₅₀) value of the fungus on the larvae of the pest was calculated as 1.03 × 10⁵ conidia ml^-1 based on probit analysis. Consequently, B. bassiana KTU-57 appears to be a significant promising isolate against the willow leaf beetle as a possible biocontrol agent.

Key words: Plagiodera versicolora, Beauveria bassiana, lethal concentration at 50% (LC₅₀), microbial control.