Emerging plant diseases (EPDs) can cause significant losses of revenue due to decreased production and the high costs of controlling epidemics. Effective control of EPDs relies on rapid detection, accurate diagnosis, timely deployment of preventive responses and containment to prevent geographic expansion. The efficiency and success of this approach depends on intricate networking and collaboration among all stakeholders, including intergovernmental and nongovernmental organizations and specialized agencies in developed and developing countries. Such cooperation also prevents the duplication of efforts and improves the use of scarce financial resources. This chapter provides insights into recent biotic threats to maize productivity and the factors driving EPDs of maize. It then highlights the requirements for a coordinated system to respond rapidly to new disease outbreaks to avert potentially disastrous consequences. The recent emergence of maize lethal necrosis (MLN) in East Africa is used as a case study.