Selection for entomopathogenic fungi and LD50 of Metarhizium anisopliae (Metsch.) Sorok. for the lesser mealworm Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

The pathogenicity of insect-pathogenic hyphomycetous isolates to the lesser mealworm Alphitobius diaperinus (Panzer) was tested in this study. Thirty isolates of Beauveria bassiana (Balsamo) Vuillemin, Paecilomyces amoenoroseus (Hennings), P. fumosoroseus (Wize) Brown & Smith, P. lilacinus (Thom) Samson, P. tenuipes (Petch) Samson, Metarhizium anisopliae (Metschnikoff) Sorokin, and M. anisopliae var. acridum were initially screened by sprinkling dry conidia onto adult A. diaperinus or by allowing adults to walk on Petri dishes with sporulating fungal isolates. The two most virulent isolates, CNPSo-Ma352 (M. anisopliae) and CNPSo-Ma356 (M. anisopliae), killed 30% and 26.7% of the dry-conidia treated adults, respectively. These two isolates were selected for LD50 bioassays. LD50 of CNPSo-Ma352 was 4.5 x 10(4) conidia per larva, and 2.1 x 10(5) conidia per adult, and for strain CNPSo-Ma356, LD50 was 2.2 x 10(4) conidia per larva and 1.3 x 10(5) conidia per adult. Larvae were 5-6 times more susceptible than adults. A larger number of conidia required to cause 50% mortality in insect evaluates, suggesting the reduced susceptibility of A. diaperinus to entomopathogenic fungi. Nevertheless, these and other strains of fungus offer an alternative method for controlling of lesser mealworm in poultry houses when associated to integrated management.