Q. What is tomato late blight?


Late blight, caused by Phytophthora infestans, is a serious disease affecting mainly tomato and potato plants throughout the world. It caused the mid-19th-century Irish potato famine. Late blight is common in New York State and surrounding states in the Northeast because our summer weather, with its cool temperatures and frequent rains, is highly conducive to disease development.

Late blight is a serious problem because the inoculum (spores) is easily carried on wind currents to infect plants in even the most remote areas in our region.  Currently all tomato and potato plants grown in home gardens and in commercial fields are susceptible to late blight!  Commercial growers have to respond to reports of the disease by spraying fungicides to prevent its spread, which otherwise would mean certain death of their crops.  Unfortunately, homeowners may not be as aware of this important disease. If no timely corrective actions are taken, home gardens can provide a source of inoculum for neighbors and for commercial interests.

For information about treating late blight and other tomato diseases, see Cornell Vegetable MD.


For tips on a variety of gardening topics, see our Plant Information Guides.
Courtesy of NYBG Plant Information Service

  • Last Updated Apr 02, 2018
  • Views 45
  • Answered By Anita Finkle

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