A classic summer activity is planting tomatoes in home gardens. Once fully grown, we cut them into pieces for salads, make homemade tomato soup and sauce, or just eat them straight off the vine with nothing but a little salt. This year, however, gardeners have had to worry about more than the occasional animals and pests trying to disturb their crops - tomatoes have been in much more danger from a silent predator known as late blight, the same disease that caused the Irish Potato Famine back in the 1840s.
Sporadic cases of late blight have been reported in past years. This summer, however, late blight spread more widely, helped by the cooler and wetter weather we experienced, especially in June. While the sun's ultraviolet rays normally kill spores being carried on the wind, the increased amounts of cloud cover we saw allowed the diseased spores to travel from field to field, infecting the crops of both farmers and private gardeners alike. The rain helped to bring the spores down onto crops as well.
Late blight spread through the Northeastern and mid-Atlantic states, all the way northward to Maine, and as far westward as Wisconsin and Illinois. Researchers from Cornell University believe the blight may have spread from tomato plants shipped from a plant company in Alabama to stores such as Wal-Mart, Lowe's and Home Depot. The tomato plants were then purchased back in April by home gardeners.
While spraying tomato crops with fungicides may save the healthy plants, once late blight has infected a tomato the end comes within only a few short days, leaving a sloppy mess in its wake, like what is shown in this picture from the Pittsburgh Post-Gazette.
Signs of late blight include dark, firm, greasy-looking lesions on the plant. These lesions will, in turn, become covered with a white fungus, in which the spores are located. The stems of the plant begin to rot away. Nickel-sized spots will appear on the leaves, ranging in color from olive green to brown. Spots will also appear on the fruit, even several days after it was picked. The Long Island Horticultural and Extension Center has a series of pictures you can scroll through to see the symptoms of late blight.
If you find tomatoes that you believe to be infected with late blight, report the possible case to your local extension office. It is important to double-bag the plant before taking it anywhere, even through your own garden, as walking around with diseased plants can spread the spores further in the wind. According to studies done by Cornell University, the unaffected parts of tomatoes suffering from late blight are not believed to have harmful side effects if eaten.
It is not yet known how much of an effect late blight has had on farmers' profits from tomato harvests this year.
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Brittany Stoner
Fox Weather Correspondent
Penn State University, Print Journalism and Spanish
