Laboratory Bioassay of Iranian Isolates of Entomopathogenic Fungus Metarhizium anisopliae (Metsch.) Sorokin (Ascomycota: Hypocreales) against two Species of Storage Pest

Abstract

Summary Th e susceptibility of adults of Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) and Oryzaephilus surinamensis L. (Coleoptera: Silvanidae) to three Iranian Isolates of the entomopathogenic fungi Metarhizium anisopliae (Metsch.) Sorokin was evaluated through bioassays with direct immersion under laboratory conditions. For each isolates, fi ve aqueous suspensions were prepared in a logarithmic series in Tween 80 (0.05% v/v). Results showed that adult of both species were susceptible to all isolates of M. anisopliae. For all three isolates, mortality percentage of the two species increased with increasing conidial concentration and signifi cant diff erence was observed between concentrations. Th e corrected cumulative mortality of adult of O. surinamensis 10 days aft er immersion ranged from 12.38 to 85.84%, 18.6 to 62.83% and 10.63 to 77.87% for diff erent concentrations of DEMI001, IRAN 715C and IRAN 1018C, respectively. Th ese amounts for T. castaneum varied from 31.07 to 74.78%, 26.02 to 75.61% and 23.33 to 89.99% for diff erent concentrations of DEMI001, IRAN 715C and IRAN 1018C, respectively. Th e parameters of probit analysis demonstrated non-overlap of 95% confi dence limits of LC 50 and LC 95 and signifi cant diff erence was observed among three isolates tested against each insect. Th e lowest and the highest LC 50 and LC 95 values were observed in the isolates DEMI001 for O. surinamensis (3/1×10 5 and 1/5×10 8) and IRAN 715C for T. castaneum (6.2×10 8 and 6.9×1014), respectively. Th is observation highlights the importance and need of screening for more virulent isolates against storage pests for use in the management of these pests.