Dr. Roberts conducts research on the detection, identification, systematics, and phytosanitary mitigation of plant pathogenic fungi and bacteria that affect foreign trade and marketability (export) of deciduous tree fruit. Research goals are to increase profitability for Pacific Northwest fruit growers and shippers by expanding existing markets and opening new markets that are currently restricted or closed because of plant quarantine issues. Concurrent research goals are to facilitate protection of U.S. agricultural production by providing accurate methods to identify and detect foreign plant pathogens that do not occur in the U.S., but which may be associated with imported commodities. Specific areas of research include: detection and risk assessment of the fire blight pathogen, Erwinia amylovora, on commercial apple fruit for export markets, and basic research on the systematics of the fungal pathogens int he genus Alternaria, which cause several diseases of deciduous tree fruit including black spot of Japanese pear, apple blotch, moldy core of apple, and Alternaria rot of sweet cherry.