Friday, September 11, 2009

Information on Tomato and Potato Late Blight

The county extension agent wrote an excellent article in our local paper about tomato and potato blight that is hitting our area. Brought on by cool and rainy weather, she said that the late blight is hitting every corner of Michigan and the Northeast. Late blight produces spores that are carried by the winds to infect the gardens. This infection rapidly kills the foliage of tomato and potato plants and can affect the fruit.

If you have infected plants, remove the plants, place in a plastic bag, seal and discard in the trash or bury the plants deep enough that they will not sprout. DO NOT put them in a compost pile because the spores can spread.

If your potato vines show signs of blight, cut off or mow off the tops before the stems get heavily infected. This helps to prevent the spores from washing down into the potato tubers. Wait to dig the tubers 2-3 weeks after the vines are completely dead to limit the number of spores on the soil surface when the tubers are dug. Be sure to get all potatoes out of the ground so that there will be no spores living in tubers and surviving the winter. Do not wash the potatoes after harvesting them until necessary as that could spread the disease.

One sigh of relief is that the blight or fungus does not live in the soil from year to year, so it should not be a problem for gardeners next spring.

The extension agent explains that the unaffected fruit of blighted plants is safe to eat. But, the National Center for Home Food Preservation suggests using only "disease-free, preferably vine-ripened, firm fruit for canning. Do not can tomatoes from dead or frost-killed vines."

If there are signs of infection on the tomato or potato, cut away the bad part. It is safe to eat the healthy part, but it is likely the fruit will deteriorate quickly due to the disease.


  1. Hi Janet,
    Thank you for the tip. I am happy to know that the blight will not survive the winter in the soil. Do you know if it stays alive only in certain types of plants like tomatoes and potatoes? Do you know if it could survive as a host in other plants like garlic or flowers?
    Thanks again!

  2. Thanks for your comment, Claudia. This late blight is particular to tomato and potato plants. It is a fungus and unfortunately, in cold, rainy weather fungus grows. Even your indoor plants show fungus when you overwater them. This was a particularly difficult year for gardeners due to the cool, rainy weather. But you know gardeners, they are always optimistic that next year will be better...!!