Late Blight

Late Blight, caused by Phytophthora infestans, is a disease of potato and tomato. It was the cause of the Irish Potato Famine which killed 1.5 million people and forced another 1.5 million to emigrate between 1845-1850. The Irish relied heavily on potato in their diet during this time, some list adult males eating as much as 15 pounds of potatoes a day. The population of Ireland was 8.5 million in 1840 prior to the blight but decreased to 4 million by 1900 due to the effects of the famine. Late Blight was chemically controlled for some time but new strains are now occurring that are showing chemical resistance.

View or download the Factsheet on Late Blight. It contains useful information about symptom descriptions and currently available control measures.

How to Submit a Late Blight Sample:

(Also check out the Sample Submission page for important additional information)
  • It is critical to get potential Late Blight samples to the diagnostic clinic as quickly as possible.
  • Avoid shipping samples late in the week. There is no delivery to campus on the weekend and the samples will overheat by Monday.
  • Place symptomatic foliage/stem samples and tomato fruit samples in a plastic bag. Blow air into the bag for cushioning and seal it with twist ties.
  • Wrap potato tubers in paper towels and place them in a paper bag.
  • If the sample can not be mailed immediately, keep the bags in a cool location (around 64 degrees) and out of direct sunlight.
As a last resort, put the sample in a refrigerator.

When submitting samples for analysis, please keep a few things in mind:

  • Always fill out the "Submission Form". Providing as much information on the form as possible will help in ensuring an accurate diagnosis of the problem. Make sure you include the form with your sample.

  • You may want to keep a copy of the form for your own records.

  • Please feel free to call the clinic with any questions prior to your sample submission.

  • For faster response, include your fax number or email address and indicate how you would prefer to receive the results.

  • Please include a check for the appropriate fee made out to Cornell University.
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