1845 Potato Blight

1845 Potato Blight STEM Famous Historical Events Nineteenth Century Life

We learn more about the potato blight which caused Ireland such misery, during the mid-19th century, from the USDA.

This image, for example, depicts what happens to the potato plant itself. But:

  • How does the fungus travel?
  • How prevalent is it?
  • How long does it take for lesions to appear (or infection to occur) from the time of first exposure?
  • Do any plants have immunity from the fungus?
  • If the fungus infects a plant, does it infect the whole plant?
  • How can we prevent it (if at all)?
  • What is the earliest-known infestation?
  • Is the fungus still a problem?

The USDA tells us more:

Route of transmission:  Phytophthora infestans form spores which can travel through the wind for at least a mile from an infected site. Spores require a host organism to survive the winter months. Infected plants material from the previous season can spread spores to uninfected plants in the current growing season. The pathogen is responsive to changes in weather, growing faster when it is humid and warm and drying off in cold weather.

Prevalence:  Potato blight can effect crops worldwide, especially areas with high humidity and moderate tempuratures.

Generation Time:  Lesions can occur within 3 to 4 days with spores forming 4 to 6 days from infection.

Immunity:  Certain varieties of potato plants are resistance to the pathogen while other plants have leaves and stems that are disease resistance, but their tubers are still susceptible allowing the plant to survive as well as provide the pathogen a host.

Morbidity:  Some plants have leaves and stems that are disease resistance, but their tubers are still susceptible allowing the plant to survive as well as provide the pathogen a host.

Methods of Prevention: The disease can be prevented by spraying fungicide on plants after periods of increased humidity and temperature. Cultivating potato varieties that are resistant to water mold is one method to combat the pathogen. However, susceptible varieties are still grown as they are commercially desirable.

When a crop is infected, all diseased material, especially the tubers, must be removed and destoryed as the pathogen can survive the change in season on infected plant materials. Eliminating the canopy through use of herbicides or strong acids two weeks before harvest can prevent tubers from being infected with blight.

Earliest Know Cases:  In 1840, the pathogen migrated from central Mexico to the United States. From North America, the pathogen spread to Europe and then to the rest of the world. In 1845 and 1846 there was an outbreak of blight in Ireland that led, along with other factors, to a famine where a million to a million and half lives were lost.

Economic Impact:  The disease, worldwide, cost 6 billion dollars annually. Many people point to the Irish potato famine or the great famine as an example of the problem with growing monoculture crops. Growing only commercial desirable varieties can lead to disease susceptibility and crop loss.

Click on the image for a better view.

Media Credits

Image and quoted information from the USDA (U.S. Department of Agriculture).


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"1845 Potato Blight" AwesomeStories.com. Apr 30, 2015. Feb 28, 2020.
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