Biocontrol is among the most promising methods for a safe, environmentally benign and sustainable pest control. Microbial pesticides offer a great potential, and it is anticipated that they will become a substantial part of the use of all crop protection products. Their development and commercialization, however, has been difficult and with many failures. In this book a rational and structured roadmap has been designed for the development and commercialization of microbial pest control products for the control of arthropod pests. The building blocks of the entire process are identified and essential aspects highlighted. Biopesticides based on entomopathogenic bacteria, fungi, viruses and nematodes are elaborately discussed. This systematic roadmap with a strong focus on economics and market introduction will assist academic researchers and industrial developers of biopesticides in accomplishing their goal: the development of successful cost-effective microbial pesticides.