The  purpose of this research was to identify the virulent isolates of Beauveria  bassiana (Bals.) Vuill. to larvae of Crocidolomia  pavonana (F.) and also to investigate the effects of  conidial concentrations on larval mortality of C.  pavonana.  This experiment was conducted at Laboratory of  Biological Control,  Plant pest and diseases Department, Faculty of  Agriculture, Andalas  University from April to October 2008. B.  bassiana were  collected from insects and soils then  cultured using selective medium.  Thirteen isolates and four  different concentration conidia(106-109 conidia/ml) were tested in the experiment. Larvae directly  inoculated  with conidial suspensions of entomopathogenic fungus. The  results  showed at a concentration of 108 conidia/ml, isolate  HhTK9 was the most virulent caused 82.50% mortality of 2nd instar larvae, with LT50 3.39 days. The mortality C.  pavonana larvae was positively correlated with by fungal  isolate and conidial concentration.Keywords:  Entomopathogenic, Beauveria bas-siana,  virulence, isolates, Croci-dolomia  pavonana 
                        
                        
                        
                        
                            
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