The effect of two entomopathogenic agents, nematodes and fungi, was tested at three concentrations and three incubation temperatures in a laboratory against fourth-instar larvae of plum curculio, Conotrachelus nenuphar (Herbst). After inoculation by immersion, larvae were statistically more susceptible to Isaria fumosorosea fungus at an incubation temperature of 5°C and to Beauveria bassiana at 25°C. Fungal concentration had no effect on mortality. More larvae were killed by nematodes at warmer temperatures and higher concentrations of either species, Steneirnema feltiae or S. riobrave. Based on preliminary laboratory results, all entomopathogens suppressed plum curculio larvae, even at low concentrations, with 35% killed by fungi and 22% by nematodes. The results are promising for further studies on control of C. nenuphar by biological agents at field conditions.