Products, termed Antheridiogen Factor (AF), and vesicle like sac formation factor (VLS-F) were present in a culture of Bacillus amyloliquefaciens strain PFR-1 grown in either a defined or simple medium. The factors inhibited appressorium development and caused the formation of vesicle like sac formation of various sizes and adventitious antheridia at the end of the germinating tubes of Venturia inaequalis spores. The factors were separated on size; a fraction less that 500 Da contain the AFand stimulated the development of antheridia at the ends of germinated tubes. Another fraction between 3 and 5 KDa contained the VLS-F and caused development of catenulate vesicle like sac of the germinating tubes of conidiospores. Preliminary characterization showed both factors resistance to boiling. AF was sensitive to Trypsin and Proteinase-K, whereas VLS-F demonstrated a resistance, to Trypsin and proteinase-K treatment.