Goss’s wilt and leaf blight is caused by the bacterium Clavibacter michiganensis subsp. nebraskense (Cmn). Historically, this disease has been a concern only to growers in western Nebraska and eastern Colorado on irrigated fields. In 2008, Goss’s wilt was reported in eight counties in Iowa and its prevalence has increased each year. In 2011, the disease was widespread throughout the central and northern two thirds of Iowa. It was also reported in a few counties in the southern third tier of counties. Why the sudden increase in the prevalence of this disease? Has the pathogen changed? Are various production practices to blame? Is seed contaminated with the bacterium? There are many questions concerning this disease.