Penicillium frequentans (Pf909) reduces brown rot caused by Monilinia spp. in stone fruit. The registration of a microbial biocontrol agent in Europe requires information on the risks and safety of a biological product. This study focused on the impact of the physical environment on Pf909 survival and growth, Pf909 mycotoxin production on fruit surface, and the Pf909 resistance to commercial antifungal compounds used in animal and human medicine. The effect of temperature (4 to 37°C), water activity (0.999 to 0.900), pH (3 to 11), light intensity (0, 90 and 180lm) and photoperiod (0/24, 12/12, 16/8, 24/0; light/dark) on mycelial growth and sporulation of Pf909 were monitored for 10days in vitro on culture medium. Antifungal activity of antifungal compounds on mycelial growth of Pf909 was also measured by a quantitative micro spectrophotometric assay after 72h of incubation. The presence or absence of four non-volatile mycotoxins (patulin, penicillic acid, ochratoxin A and citrinin) on nectarine surfaces treated with Pf909 was determined by HPLC. Growth rate was significantly influenced by water activity, temperature and light exposure conditions. Pf909 showed maximum growth and sporulation at 22°C and 25°C, in wet conditions (0.999 water activity), with a pH5.6 to 9, and in darkness or a short light photoperiod. Our results showed all antifungal compounds used reduced significantly Pf909 mycelial growth at tested commercial doses. HPLC data analysis showed that 7days after biofungicide (Pf909) application there were no mycotoxin products on the surface of nectarine. Finally, no phylogenetic relationship has been shown among Pf909 and other species of Penicillium that produce mycotoxins. In conclusion, from an ecological point of view, Pf909 would establish and survive actively over a broad range of climatic conditions. The probability of risks to human and animal health is considered very low.