Pathogenicity of Three Different Entomopathogenic Fungi, Metarhizium anisopliae IRAN 2252, Nomuraea rileyi IRAN 1020C and Paecilomyces tenuipes IRAN 1026C Against the Potato Tuber Moth, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae)

Abstract

The potato tuber moth (PTM), Phthorimaea operculella Zeller, is a prominent pest of potato in many potato cultivation areas such as Iran. Since the potato is one of the most important sources of human food, non-chemical control of the pest is essential. Application of entomopathogenic fungi is a low-risk alternative method to synthetic chemical insecticides. Therefore, we examined the efficacy of Metarhizium anisopliae IRAN 2252, Nomuraea rileyi IRAN 1020C and Paecilomyces tenuipes IRAN 1026C against neonate larvae and eggs of P. operculella under laboratory (26 ± 1 °C, 60 ± 5% relative humidity (RH) and a photoperiod of 16-h light: 8-h dark (L:D)) and greenhouse (26 ± 2 °C, 55 ± 5% RH and a photoperiod of 14-h L: 10-h D) conditions. Probit analysis of toxicity showed that N. rileyi was the most effective fungus against neonate larval penetration into potato tuber with a lethal concentration resulting in 50% mortality (LC₅₀) equivalent to 1 × 10³ conidia/ml. Moreover, adult emergence and first generation progenies of PTM were reduced when the LC₂₅ value of each fungus was used. N. rileyi showed the highest toxicity against neonate larvae, pupae and adult emergence of PTM under laboratory and greenhouse conditions with LC₅₀ values equivalent to 2.6 × 10² and 4.2 × 10³ conidia/ml, respectively. N. rileyi caused significant egg hatching reduction (LC₅₀ = 4.8 × 10⁴). The results indicated that these entomopathogenic fungi had ovicidal and larvicidal activities against P. operculella and can be used in integrated pest management (IPM) programmes.