Until recently, the US government had not considered the national agriculture and food supply system as a critical national infrastructure. Now that this omission has been officially corrected, building a framework for defending this sector from various terrorist and biowarfare attacks is under federal consideration. Vulnerability of our animal herds and crops is a sectoral concern that needs to be addressed by government in close consultation with different agricultural and food association entities, companies, and academic institutions. Some useful guidance is available from intelligence, defense and law enforcement organizations. Other guidance is available from inspections and regulatory agencies concerned with food and product safety, and inspections for prohibited products, plants and animals. Combining knowledge about naturally occurring plant diseases with knowledge on known biowarfare agents, the agricultural plant research community should be able to provide important continuing assistance for helping structure a science-based national agricultural sectoral defense plan.