Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Resurgence of the Irish Potato Famine Fungus

Authors
item Fry, William - CORNELL UNIVERSITY
item Goodwin, Stephen

Submitted to: Bioscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 2, 1996
Publication Date: N/A

Interpretive Summary: This manuscript describes the recent resurgence of the Irish potato famine fungus, Phytophthora infestans. This organism causes late blight disease of potato and tomato. After being effectively controlled in most developed countries for almost 100 years, recent changes in populations of this pathogen have lead to its global resurgence. This is partly because new migrations have spread more destructive strains of the fungus around the world from its center of origin in Mexico. These new strains have caused serious epidemics in Europe, Asia, Africa and South America beginning about 15 years ago. Another wave of migration was detected from northwestern Mexico into the United States and Canada during the early 1990s. DNA fingerprint analysis revealed that these migrations introduced at least two new strains that have caused devastating epidemics and economic ruin for many United States potato and tomato growers. These two new strains spread rapidly throughout the United States in only three years. One factor addin to the severity of these epidemics is that many of the new strains are resistant to the commonly used fungicide that previously kept the disease in check. Halting an epidemic caused by a fungicide-resistant strain is extremely difficult. In addition to fungicide resistance, these new migrations brought in the second mating type of the fungus which will make sexual reproduction possible in the United States for the first time. The spores produced by sexual reproduction can remain dormant in the soil for many years which will make the disease more difficult to control. Sexual reproduction may have occurred already in British Columbia, Canada. This paper demonstrates the damage caused by migrations of pathogenic microorganisms and poses methods to prevent such problems in the future.

Technical Abstract: Migration of the fungus Phytophthora infestans from Mexico to Europe destroyed potato crops and led to the devastating Irish potato famine during the 1840s. A century later, the disease was generally controlled by fungicides in most developed countries. However, new migrations of especially virulent and fungicide-resistant strains out of Mexico in the past two decades have caused a resurgence of the disease in Europe, Asia, Africa and South America. Epidemics in parts of the United States and Canada during the early 1990s were locally devastating, sometimes causing total crop loss and severe economic hardship for many potato and tomato growers. This well documented case study supports the view that for plants as well as for wildlife, animals and humans, introduced pathogens and new variants of old ones are a persistent threat.

Last Modified: 11/23/2014
Footer Content Back to Top of Page