Sorghum chafer, Pachnoda interrupta (Olivier) is a damaging pest of sorghum, other cereals and horticultural crops in Africa which results in complete crop loss. Currently, the management strategies rely heavily on chemical pesticides, which do not provide effective control. There is evidence showing that microbial biocontrol agents have the potential to control P. interrupta. In this study, the entomopathogenic fungi isolated from soils and insects in Ethiopia were identified using morphological and cultural characteristics. These were then evaluated for viability and virulence against Galleria mellonella (Fabricius) (Lepidoptera, Pyralidae) larvae and P. interrupta adults. Firstly, 116 Metarhizium spp. and Beauveria spp. were considered. The isolates were evaluated based on high viability as measured by percentage germination on SDA media. Only 56 isolates had greater than 70% viability. Secondly, these were further evaluated using conidial suspensions applied to G. mellonella larvae at a concentration of 1×108conidia/ml. Four Beauveria spp. and three Metarhizium spp. isolates which caused over 60% mortality were selected for final virulence assay against adults of P. interrupta. The selected isolates were further confirmed by PCR amplification of ITS4 and ITS5 gene regions and chi1 and chi4 primers. Finally, the seven isolates were evaluated for virulence against P. interrupta at a dose of 1 mg dry conidia/10 beetles under laboratory condition. Mortality of P. interrupta ranged from 14% for isolate 9604 to 82% for isolate PPRC51. Dose-response tests showed that the LD50 of PPRC2 (0.62 mg/10 beetles) and PPRC51 (0.55 mg/10 beetles) isolates were not significantly different from each other. The results demonstrated the high potential of the two isolates (PPRC51 and PPRC2) as microbial biocontrol agents. However, field evaluation of the isolates should be performed for their development into a mycopesticide against P. interrupta.
Key words: Pachnoda interrupta, Metarhizium anisopliae, Beauveria bassiana, bioassay, ITS4, ITS5.
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