Molecular Identification of Beauveria bassiana and Metarhizium anisopliae Isolates and Their Bio-control Potential against Acanthoscelides obtectus and Sitophilus Zeamais

Abstract

Acanthoscelides obtectus and Sitophilus zeamais are among the most damaging stored-product insect pests. This study was carried out to identify Beauveria bassiana and Metarhizium anisopliae and to evaluate their insecticidal potential against A. obtectus and S. zeamais adults. Fungal isolates were characterized molecularly based on ITS1, 5.8S and ITS2 regions of rDNA. B. bassiana YK23 and YK26, and M. anisopliae YK41 and YK45 were sprayed onto adults of A. obtectus and S. zeamais at 1×10⁵, 1×10⁶ and 1×10⁷ conidia mL⁻¹ doses. At the end of the 10th day of application, the numbers of dead adults were counted. Mortality rates (%) and lethal times (LT₅₀ and LT₉₀) were calculated for each isolate. Fungal isolates displayed promising insecticidal activity against A. obtectus and S. zeamais. B. bassiana and M. anisopliae caused 100% mortality against A. obtectus, even at the lowest dose. However, B. bassiana and M. anisopliae caused 100% mortality on S. zeamais at higher doses. Depending on the increasing doses, significant decreases were observed at the lethal times. Median lethal time (LT₅₀) decreased up to 64.24 h (2.67 days) and 53.69 h (2.24 days) in A. obtectus exposed to B. bassiana and M. anisopliae, respectively. LT₅₀ decreased to 61.04 h (2.54 days) and 53.89 h (2.25 days) in S. zeamais exposed to the same fungi. B. bassiana and M. anisopliae can be taken into account in the control of those pests.