The material used for composting may contain pathogenic or harmful microorganisms, therefore, it is important issue to eliminate harmful or pathogenic microorganisms during the composting process to be used in plant production. Three different mixtures were prepared at initial C/N ratio of 35.34, 40.10, and 47 fixing the apple scab infected leaves at 62% dry weight basis. Composting study was carried out using three identical cylindrical reactors made of two nested plastic containers with 65 L. Temperature, moisture, carbon/nitrogen ratio, organic matter EC, pH, and O-2/CO2 concentrations were monitored during process. Apple scab disease incidence of apple leaves and the colony number during composting, compost microbial population, and germination index of compost mixtures were determined. Except for the temperature rise to 65 degrees C for a short time at 7 days of composting for Mix-1, all temperature for three mixes stayed between 24 and 46 degrees C. Disease severity of apple scab obtained from the compost samples showed that colony of apple scab after 16 days of composting were not detected. Furthermore, the population of beneficial microorganisms such as bacteria, actinomycetes, and fungi was colonized in the finished compost mixes. Germination index at the finished compost were above 80% for Mix-1, Mix-2, and Mix-3 at 10(-3) dilution rate. In conclusion, composts obtained from apple scab infected leaves with dairy manure can be used reliably in agricultural production.