The 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, five 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 significant difference was observed between concentrations. The corrected cumulative mortality of adult of O. surinamensis 10 days after immersion ranged from 12.38 to 85.84%, 18.6 to 62.83% and 10.63 to 77.87% for different concentrations of DEMI001, IRAN 715C and IRAN 1018C, respectively. These amounts for T. castaneum varied from 31.07 to 74.78%, 26.02 to 75.61% and 23.33 to 89.99% for different concentrations of DEMI001, IRAN 715C and IRAN 1018C, respectively. The parameters of probit analysis demonstrated non-overlap of 95% confidence limits of LC50 and LC95 and significant difference was observed among three isolates tested against each insect. The lowest and the highest LC50 and LC95 values were observed in the isolates DEMI001 for O. surinamensis (3/1×105 and 1/5×108) and IRAN 715C for T. castaneum (6.2×108 and 6.9×1014), respectively. This observation highlights the importance and need of screening for more virulent isolates against storage pests for use in the management of these pests.

Merarhizium anisopliae; biological control, storage pest; immersion bioassay

Published by University of Zagreb, Faculty of Agriculture, Zagreb, CROATIA
Sponsored by Ministry Science and Education of the Republic of Croatia