Late blight in the air

Your tomatoes are at risk

By FRITZ MAYER

REGION — Hundreds of articles can currently be found online about late blight, and many of them explain that late blight is the same plant disease that caused the Irish Potato Famine in the 19th century. No one is suggesting that the current outbreak is going to result in a famine. But it is a real threat to tomato plants this year and, to a lesser extent, potato plants.

There has been at least one known outbreak in Wayne County, PA. Ed Pruss, an educator with Wayne County Penn State Cooperative Extension Office, said there was a small outbreak of the blight in a farmer’s field, but the situation has been effectively dealt with and the infected plants had been destroyed.

In Sullivan County, NY, Joe Walsh, executive director of Cornell Cooperative Extension, said that the extension has received about a dozen calls, mainly from backyard gardeners, over the past couple of weeks that reported late blight symptoms.

So how much should you worry about the tomato plants you lovingly tucked into the soil six or eight weeks ago? Well, a bit of concern might be called for.

Dr. Meg McGrath of Cornell University’s Long Island Horticultural Research and Extension Center, who is well studied in the area of blight, said that the spores that bring the disease can travel vast distances in the air. She said, “It’s a bit unpredictable how things will go. Back in 2007, late blight hit where I am here on Long Island, and the nearest known place [that had it] was Eastern Pennsylvania; that’s a pretty big jump.”

On the other hand, dumb luck can also play a role. McGrath talked with one gardener, who lost all of the tomato plants in her large garden, but two other plants that were in a somewhat sheltered area on her patio survived.

The blight has spread to all of the states in the Northeast and at least 33 counties in New York. And one reason for the rapid spread of the disease was the cool wet weather in June. The weather, it turns out, will also play a large role regarding how much the disease spreads through the rest of the season.

“If you have an overcast day, that’s when the spores can move long distances,” said McGrath, “because the clouds protect the spores from the ultraviolet radiation of the sun.” Rain at night brings the spores down. A bright sunny day kills the spores.

Many reports say that the disease was spread through infected seedlings at big box stores, such as Wal-Mart and Home Depot, through a grower called Bonnie Plants. Executives at the company insist that they’ve been blamed erroneously, that inspections have shown no infections of their seedling in their greenhouses and the infections must have happened after the plants had left the facilities.

McGrath is not convinced. She said if the company’s seedlings had been infected outside of greenhouses, other seedlings at other garden centers would have likewise been infected, and this was not the case. She added that this is the first time late blight had ever been seen in big box garden center seedlings.

There are some actions that can protect plants. Farmers can treat plants before they’re infected with various fungicide sprays. Pruss said home gardeners can buy fungicides containing copper at garden supply shops that will offer some protection, though whether this method would be considered organic would depend on the certifying organization.

It is generally agreed that once a plant is infected, it’s best to pull it and discard it, but not in the compost pile. However, McGrath said she talked to one retired gardener whose plants were hit. He got rid of the plant, and now inspects the remaining plants four times a day, pulling leaves that show anything resembling a spot of rot. He has been able to keep the disease at bay. But beating the disease once it’s in the garden is not easy.