Fungus Behind the Irish Potato Famine Strikes the U.S.

By Allison Bond | July 13, 2009 5:37 pm

blightThe fungus that caused the notorious Irish potato famine of the 1840s and 1850s is spreading among tomato and potato plants in the northeastern United States. Known as late blight, the fungus spreads easily among plants by airborne spores. This year’s epidemic has taken root at major garden retailers, eventually invading not only home gardens but also major commercial and organic farms.

The disease causes dark lesions on the plant’s leaves and stems; tomatoes then turn brown and decay, emitting a rotten odor. Although the fungus is not dangerous to people, its effects render infected plants inedible. “Late blight has never occurred this early and this widespread in the United States,” said Meg McGrath, a plant pathologist [Reuters]. Its spread has been facilitated by the cool, wet weather the Northeast has experienced this summer, along with an increased number of home gardeners looking to grow their own food as a result of the recession. This year’s blight also is particularly dangerous because of how early it appeared in the growing season; usually, the blight hits plants late, after most of the fruit has been harvested [The Baltimore Sun].

If the fungus continues to spread, consumers might see “a little less quantity and a higher price” for tomatoes as growers spend extra on fungal sprays, said McGrath…. So far, outbreaks have been sporadic but spread over a wide geographic area, with infected plants reported from South Carolina to Maine and west to Ohio [The Washington Post]. Conventional farmers can control the blight with fungicide, while those looking to grow the plants organically can combat its spread with neem oil, which must be applied weekly. 

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Image: Wikimedia Commons

CATEGORIZED UNDER: Environment, Living World
MORE ABOUT: agriculture, botany
  • Nick

    Or, just grow heirloom tomatoes that are resistant to the fungus, such as Legend.

  • http://msn roger

    Nick, the Legend tomato is not available to the general public because the patent has not yet been perfected. So said the secretary for Jim Myers (developer of the Legend) at approx. 4:45 p.m. July 14 (at Oregon State University in Corvallis OR).

    The Legend is resistant, but not impervious to the potato blight. The fruit ripens earlier than others, while the blight attacks toward the end of the season.

  • jhno

    this is the kind of thing that happens when you trust your u.s. govt and f.d.a and licence farmers and indusstry to produce genetically modified organisms and crops. BLIGHT! the famine came about in ireland because the crops that were flourishing were exported to britain
    thus leaving nothing but a failed potato which peasants had to eat , they had nothing else. some lived on berries , some knew not the difference between poison berries and edible fruit.
    we have to remember that its a very delicate system of growth and migration and evolution in nature, from the advent of intensive farming we destroyed what we have got. we havent come very far today despite claims otherwise by industry controlled govt that soon there will be enough food for everyone. alas there will be nothing to eat.

  • I love Turtles

    Capitalize please! That post reads as one incredibly long sentence and therefore’s also difficult to comprehend on the first reading much as this demonstration sentence is turning out to be…

  • Peter R. Limburg

    I am sorry to see that jhno subscribes to conspiracy theories and dislikes such niceties as capitalization and the use of commas vs. smi-colons and periods. More to the point, my own tomato plants show signs of the blight, but I am hopeful that repeated spraying with fungicides will carry them through the season.

  • David Stein

    A high tunnel which would increase the temperatures and reduce water standing on the plants could also help since fungi like water.

  • Tatyana

    The appearence of populations of Phytophthora infestans resistent to fungicide metalaxyl were connected with A2 mating type widespreading since 1980. The populations of Phytophthora infestans have clonal structure in North-West region of Russia, not sexual panmyctic. But the stem form of the diseases are dominated now. Potato cultivar ‘Nevskiy’ have tubers very resistent to late blight. Their are two resistance genes (R1R2) in this cultivar. Potato cultivar “Naiyada” resistent to leaf form of late blight. This cultivar has very stable (polygenic) resistance to late blight.


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