Abstract: The infectivity of Heterorhabditis bacteriophora for adult stage of Phytodecta fornicata was evaluated in the laboratory. Two different nematode concentrations (1000 and 2000 infective juveniles (IJs) per adult) were tested at temperatures of 22 °C and 30 °C. Mortality of insects was checked at 3 d post infection (p.i.); emergence of IJs from cadavers was noted at 8 and 11 d p.i.. For the first time, the experiment demonstrated that H. bacteriophora applied in rate of 1000 IJs per beetle is causing 100% mortality of P. fornicata, and that IJs developed inside adult insect cadavers. The effects of temperature and concentration of nematode preparation were of less importance. The harvest of IJs from cadavers was obtained but with low population level. The time of emergence of IJs was temperature dependent. In order to develop cost effective and sustainable control measure, further mortality studies on individuals, with other species and strains, and assays with more realistic environments are needed.