Late blight, the aggressive plant pathogen that ravaged the 2009 tomato crop in backyards and some commercial farms across Long Island and the northeast, is highly likely to return in 2010, a top plant pathologist said last week.

The weather, the pathologist and a top state official say, will be the key.

A hot, dry growing season on Long Island will keep the blight at bay, said Margaret Kelly, assistant director of the division of plant industry at the New York State Department of Agriculture and Markets.

While only the weather will determine whether it's as bad as last year, "There's a better than 50 percent chance, maybe closer to 100 percent," of late blight recurring, said Meg McGrath, a plant pathologist at the Cornell Horticultural Research and Extension Center in Riverhead. "It's happening in Florida right now."

Awareness of the spore-borne disease and inspections by the state Department of Agriculture and Markets, which licenses growers and nurseries, could slow or eradicate it this year.

"There's concern about this disease, so we want to make sure we're out ahead of it this year," said Kelly.

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"We are making a concerted effort to be inspecting greenhouses and stores. The concern is material coming from out of state, because it goes directly to stores," she said.

The disease does not winter over in colder climates like Long Island, but it can winter over in the south, then drift north on what botanists call a "green bridge" as the planting season and air currents move north.

Other concerns: the disease was so widespread last year that eradicating all traces is difficult - particularly in last year's potatoes, where it can linger. And experts also fear the prominence of mass-market plants, some imported from the south, could create a repeat performance of 2009. So too, they say, could lack of knowledge about the disease.

Lessons learned

Some gardeners have learned the lessons. After losing her tomato crop last year, Christine LaMonica of Wading River said she won't buy any plants from garden shops this year (she's always grown her own tomatoes but last year bought eggplant seedlings).

If she spots any of last year's potatoes sprouting, she said, "I'm going to pull them all up."

McGrath said she hopes that the blight does not debut on Long Island as early as it did last year - in late June - compared with its typical appearance in early autumn.

Wandering among this year's seedling tomato plants in his backyard greenhouse, Nick Ranieri, 70, of Mattituck, describes last year's blight.

"I have never seen such a thing happening in my garden," said the retired electrician, an Italian immigrant who has farmed and gardened all his life. "It was very sad, the saddest thing." His crop of 40 plants was wiped out, a major disruption of the family lifestyle that depends on canned tomatoes through the winter.

A recurring problem

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The disease, known as Phytophthora (Latin for "plant destroyer") is transmitted in the air on wet, sunless days (spores are killed by UV light), conditions that were frequent in 2009.

Since Cornell began keeping records on late blight in 1988, it has been seen here in each of the past four years and 2002, Several plants can be a host for the spores, including Petunias, and spores can jump between potatoes and tomatoes. Infected plants can quickly spread the disease if they are not removed and isolated - experts recommend cutting away affected leaves, or the entire plant, depending on the extent of the blight.

Another problem: New specifically late blight resistant varieties of tomato plants have been developed, but won't be widely available until next year.

It wasn't just that the cool wet summer weather that encouraged the late blight in 2009.

Last year's outbreak was blamed on mass market retail stores that bought plants from wholesale growers, some from the south where late blight pathogens can winter over. The University of Massachusetts Plant Diagnostic Laboratory, noted that "infected plants were distributed through large local retail stores throughout the region (Ohio to Maine). Never before has such an extensive distribution of infected plants occurred."

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But Lois Chaplin, director of marketing for Bonnie Plants, the Union Springs, Ala., company that supplies big retailers like The Home Depot and Lowe's, questioned that association.

"Good growers always have precautions in place," to control disease, she said. "There are things that happen in nature we can't control, but any good grower will have programs in place to prevent the problem."

As for whether she expects 2010 to see a return of last year's devastation, she said, "I don't think it's necessarily any different from any other year."

She noted that Bonnie has 78 satellite shipping/growing facilities around the country, including at least three in and around New York State, so there is no reason to import plants from as far away as Florida.

McGrath of Cornell said it's unfortunate that government or agricultural interests didn't do an exhaustive study of 2009 late blight to determine what specifically caused it, given the devastation it caused.

Business as usual

Jim Trowbridge, operations manager at the Lowe's home center in Medford, said it's business as usual in the garden department. Tomato plants and seeds are already on shelves and staffers will recommend fungicides as a preventive measure, if customers ask. The stores aren't taking any drastic measures on late blight prevention, Trowbridge said, noting that the grower, Bonnie, conducts quality control at its centers.

Suspicions that tomato plants from big retailers caused the 2009 outbreak do not seem to have had an impact on this year's sales.

"Sales have already taken off," said Trowbridge. "We have people literally waiting for the [plant] truck to show up."

McGrath said lack of education is late blight's biggest ally. Most big farmers know how to spot it, and will spray crops if they know the disease is spreading nearby. "I'd be more concerned about being in an area where all the neighbors have gardens," she said. "Do all of them know about late blight?"

Ranieri, the Mattituck gardener, is a case in point. Last month, he planted potatoes from last year's backyard harvest. Told that Cornell advised against it, he said, "I wish I had known that three weeks ago."