Fruits and Vegetables Under Siege

By Sara Lipka
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Photo by Sara Lipka


Plant diseases don't make sexy headlines. Downy mildew and brown rot? Most people are indifferent. But this growing season a vicious fungus spread across East Coast gardens, farms, and news media. Late Blight Devastates Tomato Crops! Even Martha Stewart got it. And even the New York Times op-ed page proclaimed the havoc.

New Morning Farm, in south-central Pennsylvania, lost 90 percent of its tomatoes. With spores proliferating throughout a cool, wet June, late blight hit early and hard. Phytophthora infestans, the nasty fungus that causes the disease that attacked the tomatoes, infects potatoes, too--in fact, late blight caused the Irish potato famine--and this year New Morning saw half that crop succumb. The farm's eggplant and pepper patches also showed signs of sporulation, but, luckily, those veggies emerged unscathed.

Tomatoes took the brunt--and became a story. Juicy reds, yellows, and purples, destroyed by fungus. Luscious summer mouthfuls, gone, and for New Morning, a 95-acre organic farm, $90,000 lost. Jim Crawford, the farm's owner, turned to his organic growers' cooperative for tomatoes--please, any tomatoes--to bring to market. Buying neighbors' crops at wholesale and reselling them retail helped, Crawford said, but it hardly covered his shortfall. As for why some tomatoes survived while nearby farms' shriveled, we'd need a mathematical model. Spores in the wind. Good luck graphing that.

Now, nippy nights assure us that the seasons are turning, and rather than diseases, we're anticipating that all-powerful annual killer: frost.

The challenges of plant pathology are lost on most produce eaters, even hip farmers' market types. But as late blight decimated tomatoes this year, it raised awareness of the natural hazards farmers face--and how hard it is to counter them, especially organically. Some of Crawford's customers inquired, sympathetically, about late blight. "Quite a few were aware of it," he said. "They read the paper."

When our customers asked, I tried to explain the distinction between early and late blight. Early isn't just an immature onset of late; the diseases are actually caused by different fungi. Fortunately for us, our first planting of tomatoes got only the milder early blight. The plants bore fruit for a few weeks, then quickly withered, the leaves all crackly brown. With three plantings of tomatoes in the field, we made sure to harvest from the newest plants first, to keep our dusty, gummy tomato fingers from becoming disease vectors.

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Photo by Sara Lipka

Still, our second planting started to look sickly. There wasn't much we could have done--certified-organic copper and conventional fungicides are most effective preventively--but we were curious. The diagnosis, from the lab: septoria leaf spot. Practically, that means we should, at the end of the season, clear all residue from the tomato field and disinfect our stakes. Fancifully, it means we have another melodramatic malady to bemoan during hours of harvesting. Itchy eyes? Must be the septoria. Better take a break.

Our other epidemic this growing season has been bacterial wilt, a disease spread not by spores, but by tiny winged villains. Back in June we worried that yellow-and-black cucumber beetles were transmitting wilt from infected plants, so we heaped all our dying cukes into a wheelbarrow and hauled them away. Then we tested for the disease by placing a small cutting from a sick plant into a glass of water. The liquid was supposed to get milky. When it didn't, we blamed the withering on squash vinebor, an insect that sucks fluid from plants' stems. Still tricky to control, but not contagious. Alas, we were right the first time. Lab tests confirmed the bacterial wilt, as did our fast yellowing field of winter squash.

We cursed the cucumber beetles, spraying organic neem oil to try to foil them. And good news: the butternut squash and pumpkins, among other crops, managed to mature before wilt shriveled the plants. Pies, soups, cornucopias, and jack-o-lanterns, saved!

Now, nippy nights assure us that the seasons are turning, and rather than diseases, we're anticipating that all-powerful annual killer: frost. The first day of fall we started a frost pool, with guesses ranging from October 10 to the 24th. My early pick, the 13th, is selfishly wishful. No more harvesting tomatoes! No more wicked ragweed!

Plant diseases still come up, but at this point we're talking about clearing our fields properly to minimize risks for next year. We're also--and this is very important--planning our Halloween costumes. If the point is to scare people, dressing as plant diseases (or parasitic weeds) should certainly frighten our fellow farmers.

This article available online at:

http://www.theatlantic.com/health/archive/2009/10/fruits-and-vegetables-under-siege/27596/