XVI International Botanical Congess

Non-indigenous fungi have an impact on U.S. agriculture. Cultural practices such as host monoculture and control strategies exacerbate the ability of introduced fungi to cause significant losses. The main pathways for introduction of pathogens are propagative material, including seeds and nursery stock, as well as raw wood and wood products. Deciding which fungi may be damaging is often difficult because we know so little about the biology of plant-inhabiting fungi, and pathogenic capabilities can be difficult to predict for non-obligate pathogens. When biological characteristics of fungi are reflected in fungal systematics, it is possible to recognize non-indigenous fungi that threaten U.S. agriculture and differentiate them from similar non-pathogenic fungi that pose little risk. Emerging diseases, such as newly discovered powdery mildews on economically important crops, provide opportunities to determine modes of introduction and insights into genetic changes that occur in pathogen populations when introduced into new geographic areas.