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Jul 232009
 

By Christopher Peake
Green Right Now

“Just the thought of tomato blight sends fear into the heart of every farmer.”

Those are the words of organic farmer Charlie Reid, who operates two small farms in southeastern New Hampshire. “We’ve been lucky this year … so far,” says Reid. “Lots of farmers have had to pull (dig up and destroy) their entire tomato crops. But with all this rain and so little sun my luck could change (for the worse) overnight.”

Blight is a highly contagious fungus that hits both tomatoes and potatoes. The Potato Famine in Ireland in the late 19th century was caused by blight. And now blight is killing both tomato and potato crops in New England and in some mid-Atlantic states. It’s not yet an epidemic, but cause for concern for both farmers and consumers, as well as home garden growers who unwittingly used infected seedlings.

The Vermont Agency of Agriculture’s “Agriview” has this alert for farmers:

“It (blight) appears on potato or tomato leaves as pale green, water-soaked spots, often beginning at leaf tips or edges. The circular or irregular leaf lesions are often surrounded by a pale yellowish-green border that merges with healthy tissue. Lesions enlarge rapidly and turn dark brown to purplish-black. During periods of high humidity and leaf wetness, a cottony, white mold growth is usually visible on lower leaf surfaces at the edges of lesions.”

There are two culprits in this year’s late blight: too much rain and consumer nurseries selling starter plants, which unwittingly spread the ailment.

Tomatoes Need Sun To Shake Blight

Rainfall has varied across the country at seemingly excessive rates: for example, too little in Texas and too much in the Northeast. While early blight in lesser amounts  is normal each year, this season’s heavy rains have soaked many farms and there hasn’t been enough sun to dry the fields.

Add wind to the rain and the situation worsens: Late blight spores are carried by wind from one plant to another. And while one plant might be infected and the one next to it untouched, eventually the entire crop in a field or backyard garden will be affected and die.

Although nothing can save your tomatoes once they become blight-infected there are a wide variety of preemptive organic and natural ways to prepare your crop. Go to Garden Web to start your search.

Organic farmers and organic home gardeners can also find natural and organic compounds at most feed and hardware stores.  Conventional farmers try to prevent blight by spraying with herbicides, fungicides and pesticides but even they don’t guaranteed success.

A second blight culprit this summer was the mass marketing of tomato plants sold at big-box stores like Wal-Mart, Lowe’s and Home Depot. An unknown number of plants were distributed by these stores via Bonnie Plants, a wholesale gardening company in Alabama that buys many of its plants from growers in other parts of the country.

Bonnie Plants has recalled seedlings that remained on store shelves but it was too late for others that had been bought and planted earlier.

Bonnie’s General Manager Dennis Thomas told the New York Times that only five of the recalled plants had blight. “This pathogen did not come from our plants,” he said. “This is something that has been around forever.”

Bonnie explains on its website that this year’s blight was worse than in previous years because of cool, wet conditions and refers home growers to the Texas A & M horticulture website, Aggie Horticulture, and its section on tomato problems. The notes on late blight help gardeners identify diseased plants; other tomato diseases are covered in the tomato guide at well.

An article in Growing Produce by a Cornell professor of plant website about this issue reports its discovery in commercial fields in Long Island in June, followed by reports on plants in retail stores.
The article notes that the problem could spread, depending on the weather: “All tomato and potato crops are at high risk of developing late blight this season, especially if the rainy weather continues. All growers should assume their crops eventually will be affected and thus should be on a weekly schedule to both thoroughly inspect their potato and tomato plantings…,” writes Margaret Tuttle McGrath.

Home Growers Should Dispose of Affected Plants

“We are urging home gardeners, especially those who may have recently planted tomato seedlings from a big box store, to check for this disease,” said Jim Dwyer, University of Maine Potato Specialist. “Because the tomato fruits will be ruined by this fungus and the threat of late blight spreading to potatoes, home gardeners that find late blight on their plants should pull, bag and throw out these plants. They should not put them on the compost pile.”

According to Jon Turmel, Vermont State Plant Regulator, “The stores across the state have been more than helpful at removing plants from their shelves.”

This summer in New Hampshire field tomatoes are selling for around $2.45 a pound but continued rain there and in Maine and Vermont hold the key to late blight and New England’s tomato crop. In the Hudson Valley agricultural region of New York late blight has been described as “explosive” and “never seen … on such a widespread basis.”

Late blight has not been common in New England but when it does occur it is very destructive. In Colchester, Vt., Laurie Mazza is still selling her greenhouse tomatoes for $2.99 a pound. “We’re a week or so away from our field tomatoes and while they look good now, especially the cherry tomatoes, something could happen.”

(Photos of healthy tomatoes and plants by Green Right Now.com; late blight tomato, photo credit: Texas A&M University)

Copyright © 2009 Green Right Now | Distributed by Noofangle Media