Fungal infection strikes region's tomato plants

Home gardeners need to inspect their tomato plants for late blight.

Tomato plants at large retail outlets, such as Lowe's, Home Depot and Walmart, are being pulled from shelves across the Northeast as the fungus spreads.

Late blight is caused by the fungus phytophthora infestans and is a serious disease affecting mainly tomato and potato plants.

The fungus causes nickel- to quarter-sized brown or black lesions bordered by white fungal growth that contains spore cells, or inoculum. Individual plants are killed quickly.

Susan J. Gwise, horticulture educator at Cornell Cooperative Extension of Jefferson County, said tomato plants at large stores in the area were pulled Monday.

She said those who bought tomatoes at small greenhouses or grew them from seed should not be affected by the original spread, but the fungus spreads quickly by airborne spores.

"No tomato plants are resistant to the disease," she said. "Infected plants need to be destroyed."

The blight is not dangerous to humans, so the tomatoes can be eaten once the infected area is removed.

Plant pathologists at Cornell University, Ithaca, first found the fungal infection in southern New York.

According to a report from plant pathologist Thomas A. Zitter, the blight spreads quickly during cool, rainy summers.

Homeowners may use fungicides that include chlorothalonil to prevent infection. These products are effective only if used before the disease appears and should be reapplied every week if wet weather persists. For organic growers, the options are very limited, since only copper fungicides can be used, and they are not very effective.

Dani F. Baker of Cross Island Farms, Wellesley Island, said organic growers try to defend against fungal infection. She said they plant in raised rows, with plenty of room between plants and rows aligning with normal wind movement.

"Healthy soil has natural enemies of things like that in it," she said. "It helps plants resist this kind of disease."

Commercial growers use the preventive copper-based fungicides.

Plant vendor Bonnie Plants, which supplies many of the tomato plants for Lowe's, Home Depot and Walmart, grows much of the New York supply of tomatoes at a facility in New Berlin.

Dennis A. Thomas, general manager, said the facility had a clean inspection two weeks ago and a second inspection Monday that discovered five plants with spots.

"There's no possible way to know where it comes from," he said. "Our plants are sprayed on a regular basis."

He said hundreds of thousands of plants have been pulled from shelves and discarded as a result of the outbreak.

Bonnie Plants' New Jersey facility received a clean inspection Monday and is shipping tomato plants to the New York City area.

Late blight occurs every few years to a decade. But Mr. Zitter wrote that this outbreak is extraordinary because of the broad region covered — from Ohio to Maine — and the early time in the season it has been reported.

Walmart is offering refunds to customers who purchased tomato plants, said Caren S. Epstein, director of public relations and brand reputation.

Mrs. Gwise said gardeners should inspect their tomato plants daily. Infected plants should be disposed of in plastic bags. Composting the plants will allow spores to spread.