Cereals are challenged by many fungal and bacterial diseases, some of which can be most destructive, threatening food security and, when considering mycotoxin accumulation, also food safety. The application of antifungal and antibacterial chemicals, the development of resistant varieties and culturing methods have been used to contain the various diseases were until recent sufficient. However, resistance breaking, pathogen insensitivity toward chemical protection, and the banning of pesticides due to environmental and health concerns have turned things in favor of the pathogens. More emphasis will therefore be put on integrated pest management approaches, in which biological control may play an important role. This chapter discusses the application of biological entities and the responsible mechanisms to protect cereals against pathogenic fungi and bacteria, some of which were already discussed and applied well before the time of chemical pesticides, and their problems with respect to efficacy and durability.