Black soldier flies (BSF) (Hermetia illucens, Diptera: Stratiomyidae) are produced on a large scale using various production methods and food substrates. This chapter reviews organisms that have true pathogenic relationships with the BSF which could cause negative effects on insect culture. These includes viruses, bacteria, fungi, protists and nematodes. The chapter looks at how managing rearing conditions can reduce disease risk as well as specific disease prevention and control measures.