Are Tomatoes with Late Blight Safe to Eat?


“A week ago the foilage of my plants showed initial signs of late blight. I trimmed the infected foilage and conintued my weekly fungcide spray. Several days later, I trimmed the foilage again. Several days after that when more foilage showed signs of the disease, I picked the unripe fruit (three bushels) thinking that if it didn’t show any signs of the disease after it ripened, it would be safe to eat and can. However, someone told me that it’s unsafe for human consumption even if it doesn’t show any signs. Is this true? I removed the plants and destroyed them. Is there anything I can do to safeguard next year’s harvest? B.”

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Late Blight Tomato

Thanks for your email regarding late blight in tomatoes.  First things first: the fruits are safe to eat!

You did the correct thing by picking the fruit – just in case!  As long as the fruit does not have many bad spots, it is okay.  There is no type of toxin in the fungus.  The only thing I do not recommend is canning them.  While the fruits may look perfectly fine, there is the possibility that the presence of the fungus in the plant has raised the pH level in the tomato.  Canning tomatoes is based on having the natural acidity of the fruit – having an inflated pH would create problems with keeping the fruit from spoiling.  If you do intend to put some of your tomatoes up for winter storage, use freezing or dehydration instead.

The pathogen that causes late blight, Phytophthora infestans, is more severe in cool, wet years. Disease-resistant varieties exist but may not always be practical given customer preferences. The fungus can overwinter in the soil if there is any plant material left in it – this can be anything from a potato tuber to an old eggplant or tomato or even a petunia plant (as they are all in the family Solanaceae).

Fixed copper compounds used to control bacterial spot and late blight foliar infections will prevent fruit rot as well.  These can be obtained from your local garden center.

© Mertie Mae Botanics LLC and Horticulture Talk!, 2009. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Mertie Mae Botanics LLC and Horticulture Talk! with appropriate and specific direction to the original content.

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