Phytophthora infestans

Phytophthora infestans is a microorganism that is known to cause the serious plant disease known as late blight. This disease is particularly destructive to potato and tomato crops, and was responsible for the Irish Potato Famine in the mid-19th century.

History

The first recorded instance of late blight was in the United States in 1843, but it was the Irish Potato Famine from 1845 to 1852 that brought the disease to worldwide attention. The famine was caused by a strain of Phytophthora infestans that was particularly virulent, leading to the death of approximately one million people and the emigration of another million from Ireland.

Biology

Phytophthora infestans is a member of the Oomycetes, a group of microorganisms that are similar to fungi but are actually more closely related to algae. The organism reproduces both sexually and asexually, and can produce large numbers of spores that are easily spread by wind and rain.

Disease Cycle

The disease cycle of Phytophthora infestans begins when spores land on the leaves of a susceptible plant. The spores germinate and penetrate the leaf tissue, where they grow and reproduce. The resulting infection causes the leaves to develop dark, water-soaked lesions. As the disease progresses, the entire plant may wilt and die.

Management

Management of late blight involves a combination of cultural practices and chemical controls. Cultural practices include crop rotation and the use of resistant varieties. Chemical controls include the application of fungicides. However, the effectiveness of these measures can be limited by the ability of Phytophthora infestans to rapidly evolve resistance to fungicides.

See Also

• Plant Pathology
• Potato Diseases
• Tomato Diseases