The USDA, Agricultural Research Service, Foreign Disease-Weed Science Research Unit has two distinct missions united by a common relationship to plant pathology and the unit's unique P-3 plant pathogen laboratory and greenhouse containment facilities.

The mission of the foreign disease program is to develop techniques for the rapid detection and identification of new and emerging crop pathogens.  Research is conducted to provide fundamental information on emerging pathogens for risk assessment and the development of practical phytosanitary regulations for the import and export of agricultural commodities and germplasm.

The mission of the weed biological control program is to collect foreign pathogens overseas from weeds in their native habitat, and to evaluate, characterize and release the pathogens in the U.S. for biological control of introduced weeds, leading to improved, sustainable weed control practices in agricultural systems with reduced dependence on chemical herbicides.