Bacterial wilt pathogen Ralstonia solanacearum is known to infect hundreds of plant species including economically important crops such as tomato, potato, pepper and banana. The disease is widespread in tropical and subtropical areas of the world and with the globalization of agriculture, plant pathogens are frequently moved into new environments. Bacterial wilt can be disseminated via a variety of hosts including high dollar value ornamentals such as geranium, anthurium, and pothos. Most bacterial wilt strains are limited in their range by temperature; however, a concern has always been that cool tolerant strains of R. solanacearum might be introduced and spread into potato and tomato production areas in North America. Due to their potential to cause major economic damage, cool tolerant Race 3 Biovar 2 (R3B2) R. solanacearum wilt strain has been designated as a Select Agent under the U.S. Agriculture Bioterrorism Protection Act of 2002. Using molecular techniques and environmental chamber studies, we have been able to identify additional Race and Biovar populations of R. solanacearum that are cool tolerant and have the ability infect tomato under cool temperature conditions. By comparing the proteomics profile of different strains of R. solanacearum, including R3B2 and other strains able infect plants at 18°C, we have identified a number of candidate proteins with functions related to pathogenicity at low temperatures. We are currently comparing total genome sequences of cool tolerant strains to identify regions that might contribute to virulence at low temperatures.