Bioassays were conducted to test two isolates of Metarhizium anisopliae (Metschnikoff) Sorokin (IMI 350 394 and ZBW 9501) against adult Heteronychus licas Klug. In a bioassay, spore suspensions in distilled water of isolates IMI 350 394 and ZBW 9501 and a granule formulation of isolate ZBW 9501 were tested against fed adult beetles in plastic vials containing heat-sterilized soil at rates of 9.5×10 6, 1.1×10 7 and 1.2×10 8 conidia/insect, respectively. Whereas, no mycosed cadavers were recovered from the control treatment, the three fungus treatments caused 5, 10 and 35% mycosis, respectively, 22 weeks after inoculation. In another bioassay, the granulated fungus isolate ZBW 9501 was also tested against fed and unfed H. licas larvae in plastic vials containing heat-sterilized soil at the rate of 1.2×10 8 conidia/larva. No mycosed cadavers were recovered from the control treatment, but the fungus treatment recorded 34 and 24% mycosis for fed and unfed larvae, respectively, 16 weeks after inoculation. For both larvae and adults the fungus-induced mortality period ranged from 2 to 16 weeks. The granulated fungus isolate ZBW 9501 applied in a small field trial at the rate of 8.2×10 12 conidia/ha had no measurable impact on the pest ( p>0.05). The paper discusses some of the possible reasons for the poor efficacy and concludes that the isolates tested are probably weakly pathogenic and more virulent isolates with a greater epizootic potential must be identified before field testing.