Plants are host to a large amount of pathogenic bacteria. Fire blight, caused by the bacterium Erwinia amylovora, is an important disease in Rosaceae. The principal and most susceptible hosts are in the sub-family Pomoideae of the family Rosaceae. The following plants are considered as important hosts, from both economic and epidemiological points of view: Amelanchier alnifolia, A. canadensis, apples, Chaenomeles spp., Cotoneaster spp., Crataegus spp., Cydonia spp., loquats, medlars, pears, Pyracantha spp., Pyrus amygdaliformis, Sorbus spp., Stranvaesia davidiana. The ability to release products with antimicrobial activity is the major mechanism by which pseudomonads suppress pathogens. Pseudomonas is a diverse genus known for their ubiquity in the environment and production of secondary metabolites. Some pseudomonad strains are well-suited to be biocontrol agents, producing a wide range of bioactive metabolites. The general antibiotics produced by Pseudomonas include phenazine derivatives, pyoluteorin (Plt), pyrrolnitrin (Prn), hydrogen cyanide (HCN), 2,4-diacetylphloroglucinol (DAPG) and insect toxin. The present study confirm the potential of Pseudomonas aureofaciens CNMN-Pb-05 strain to be used as active ingredient of microbial biopesticides for fire blight control that could be eventually extended to other plant bacterial diseases. Experiments were done under controlled environmental conditions on detached flowers, in order to determine the effect of Pseudomonas aureofaciens CNMN-Pb-05 against E. amylovora infections. The plant material was obtained from a commercial orchard near Chisinau, and transported to the laboratory under refrigeration, and used before 24 h. Individual flowers were maintained with the cut peduncle submerged in 10% sucrose solution. Flowers were sprayed with suspension of Pseudomonas aureofaciens CNMN-Pb-05 at 1×107 CFU ml−1 (0.4–1 ml per flower) using a micro sprayer. All materials were introduced in plastic boxes in a controlledenvironment chamber at 25 °C (±1°C), high relative humidity, and 16 h of light - 8 h dark photoperiod. After 24 h, the hypanthia of flowers were inoculated with 10 μl of a suspension of E. amylovora PD 4072 at 1×107 CFU ml−1. The inoculated plant material was again incubated under the above mentioned conditions for 5 days. The experimental design consisted of three replicates per treatment with per replicate. Controls treated with water and inoculated with the pathogen were included. Incidence of infections was determined at 5 days. Results were expressed as cells or CFU per blossom using Fisher’s least significant difference test (P≤0.05). The installation of Pseudomonas aureofaciens CNMN-Pb-05 strain on detached blossom before the inoculation with E. amylovora (preventive treatment) allowed an efficient control of disease (98%), with an incidence that never exceed the level 3.2%, but for curative treatment the incidence increased to 38.4% and the efficiency was 57.6%. Under field conditions, Pseudomonas aureofaciens CNMN-Pb-05 applied twice (10 and 75% bloom time) at 107 CFU/ml reduced significantly the incidence of fire blight by 69.2%. The antagonistic strain was able to reduce significantly the incidence of infections of E. amylovora compared to non-treated control, where the severity of disease attack was 1.33%. Results from this work illustrate that Pseudomonas aureofaciens CNMN-Pb-05 strain was able to control efficiently fire blight in apple trees under the conditions of the arias of Moldova.