In response to consumer environmental and health concerns concerning chemical pesticides, more attention has been placed on the development of biological control agents for the mitigation of postharvest diseases. However, postharvest biocontrol products are not currently widely used due to variable efficacy. The purpose of this study is to determine the potential effectiveness of certain biological agents (Bacillus spp.) in the control of preharvest (foliar apple scab) and postharvest (bitter rot) diseases in apples. Golden Delicious and Rome Beauty cultivars were assessed weekly for apple scab in a preharvest test. Upon harvest, the apples were wounded and inoculated with bitter rot and monitored over eight days. Treatment groups included: preharvest application of Bacillus spp., no preharvest application, post-harvest application of Bacillus spp., and no postharvest application. Applications of Bacillus spp. In May or May and June reduced apple scab most effectively, while postharvest or postharvest plus preharvest application reduced the size of bitter rot lesions significantly. Additional research is needed to determine the most effective timing and rate of application.