The most feared tomato disease is spreading across parts of the country, infecting plants and causing panic among backyard gardeners, farmers, and supermarket managers alike. After all, tomatoes are centerpieces in many gardens and major moneymakers for farmers and supermarkets. But now the same disease that caused the Irish potato famine of 1845 threatens tomatoes—particularly organic ones—in 2012.
Late blight is a hard-to-manage disease caused by a funguslike pathogen that also targets potatoes. In fact, it's believed that recent outbreaks most likely stem from contaminated seed potatoes or potato tubers that were tossed in a pile, survived the mild winter, and sprouted this spring, full of disease-causing late-blight spores. Spotting late blight early isn't always easy, either—it resembles other tomato plant problems like drought stress, early blight, Septoria leaf spot, and gray mold, making it hard for gardeners to make a positive ID.
The once-rare disease annihilated tomato crops in 2009 and is once again spreading along the Eastern seaboard, with verified occurrences in Florida, North Carolina, Virginia, Pennsylvania, New Jersey, and New York. The bad news? A wet and humid spring has provided perfect conditions for the disease to flourish very early in the season. "It's kind of like the cancer or AIDS of the vegetable disease world," says Meg McGrath, PhD, plant pathologist at Cornell University's Long Island Horticultural Research & Extension Center.
But wait! There's good news, too! There's still time to control it, and the fate of this year's tomato crop lies in the hands of backyard gardeners and farmers, since early detection and removal of infected plants have the ability to stop the nasty disease in its tracks. "This is a community disease because it is so contagious and destructive. We all need to work together to manage it," says McGrath. "An outbreak cannot be left unmanaged, no matter how small, due to the potential impact on others growing these crops."
A blow to organic farmers and gardeners
Organic tomatoes are more at risk, since conventional farmers and gardeners are able to use more potent fungicide chemicals to prevent the disease from taking hold in their plants. The problem is, those systemic chemicals can also wind up inside of your food, potentially harming your health.
While certain copper products are approved for use in organic production, copper can build up to unhealthy levels in your soil, cause eye damage, and kill beneficial insects that help create biodiversity in the garden. McGrath said other approved-for-organic products, such as Regalia and Actinovate, appear safer.
What Does Late Blight Look Like?
Get ready to pay more for organic tomatoes
If late blight continues to spread, as it did in 2009, you'll likely be paying more for organic tomatoes—and you should, according to McGrath. Tomatoes are a cash crop for many farmers, and continually losing a tomato crop to late blight has the potential to put farmers out of business because a market stand without tomatoes is one that some customers will pass by. Aside from that, sustainable farmers put a huge amount of labor, time, and expense into nurturing tomato crops. "You put so much effort into tomatoes, and then to lose them before you've got anything harvestable, it's tough. It's tough to watch," McGrath says, adding that she's seen farmers cry when they receive a late-blight diagnosis. "It's a disease that brings out emotions you don't usually see."
Got a garden? You need to:
1. Inspect plants regularly, and take samples of any plant with symptoms you suspect are late blight to your local extension right away for diagnosis. Tianna DuPont, sustainable-farming educator with Penn State, says late blight will have greasy gray-tan-colored lesions. When scouting for the disease—something gardeners should try to do once a day—look for fuzzy growth on the underside of leaves. Another clue is late blight tends to develop randomly on the plant, and not only on the bottom leaves, she says.
Download Late Blight Identification Brochure
2. If late blight occurs in your plants, properly destroy the affected plants.
3. Gauge your risk by monitoring your region. Check the USAblight project, which tracks national late blight occurrences. "If we all work together we can prevent a major epidemic from developing," McGrath says. "It absolutely can be controlled if everyone is on top if it."