This year’s Northeast tomato crop has been causing distress for some growers. Late blight is a common disease in tomatoes caused by the fungus Phytophthora infestans.

The disease thrives in cool, moist conditions and can wipe out an entire tomato crop within just a few weeks of infestation. Unfortunately, during the past months, our weather has been ideal for late blight.

In the beginning, infected tomato plants develop water soaked lesions on the leaves and stems.

Under cool and moist conditions, the fruits may become infected initially with firm, dark brown lesions that rapidly become enlarged, wrinkled, and somewhat sunken.

The rotted areas are usually located on the top of the fruit and may remain firm or become mushy.

Both green and ripe fruits can be infected. Green fruit that is picked early and ripened indoors may develop symptoms before it is ready to eat.

Penn State recommends that canners select only disease-free, preferably vine-ripened, firm tomatoes for canning. Fruit that shows severe symptoms of late blight, especially tomatoes that have mold inside the tomato, should not be used for canning.

According to Penn State faculty member Dr. Luke LaBorde this does not mean that the fungus itself is harmful to eat. However, they are not recommended for canning.

Also, tomatoes that are damaged by frost are also not recommended for canning because the softened tissue may be quickly invaded by fungus.

Even then, tomatoes from blighted plants need extra care. Cut all black or brown spots from the tomatoes and keep only the firm flesh of the fruit, he said.

If spores from the blight are eaten they will not cause physical harm, but they could have a negative impact on the long-term quality of preserved tomatoes.

Penn State also does not recommend diseased tomatoes be used for freezing. The disease organism by itself is not harmful to consume. However, the tissue damage and elevation of tissue pH that occurs can create conditions that promote the growth of other potentially harmful microorganisms.

Although Penn State recommends using only vine-ripened fruit for canning, tomatoes that have been picked green and allowed to ripen indoors may be canned if they show no symptoms of late blight.

One important step in canning tomatoes is adding lemon juice or citric acid per quart of tomatoes. We call this acidification.

Today’s tomatoes are lower in acidity then those of yesterday years. To can your tomatoes safely in a water bath, the pH of the tomato must be 4.6 or lower.

To be safe, Penn State recommends adding more acid to the quart or pint of tomatoes before canning.

To ensure safe acidity in whole, crushed, or juiced tomatoes, add two tablespoons of bottled lemon juice or 1/2 teaspoon of citric acid per quart of tomatoes.

For pints, use one tablespoon bottled lemon juice or 1/4 teaspoon citric acid. Acid can be added directly to the jars before filling with product. Add sugar to offset acid taste, if desired. Four tablespoons of 5 percent acidity vinegar per quart may be used instead of lemon juice or citric acid.

For a free fact sheet on canning tomatoes safely, call our office at 602-0600 and request a copy of the “Let’s Preserve Tomatoes.” Or feel free to consult the Penn State Food Preservation web site at http://foodsafety.psu.edu/preserve.html for more detailed directions on canning tomatoes and other foods.

To celebrate the upcoming Pittston Tomato Festival try this recipe healthy recipe that is quick and easy, yet very flavorful.

Baked Greek Tomatoes

2 large ripe tomatoes, halved

1 slice whole wheat bread, crusts removed

2 Tbsp. grated Parmesan cheese

1 garlic clove, finely minced

1 tsp. olive oil

1 tsp. dried oregano

1/2 tsp. dried basil

1/2 tsp. dried thyme

Salt and freshly ground black pepper, to taste

Preheat oven to 350 degrees.

Gently squeeze tomatoes or use a spoon to remove seeds.

In blender or food processor, make crumbs of bread.

In small bowl, combine bread crumbs, cheese, garlic, oil, oregano, basil, thyme and salt and pepper, to taste.

Spoon crumb mixture into each halved tomato. Place tomatoes in casserole dish.

Bake uncovered 25-30 minutes, until tomatoes are soft, but not mushy, and topping is golden brown.

Makes 4 servings.

Source: American Institute for Cancer Research

About the Author

Mary R. Ehret, M.S., R.D., L.D.N., is with Penn State Cooperative Extension, Luzerne County, 16 Luzerne Ave., West Pittston, Pa., 18643. (570) 825-1701/602-0600. Fax (570) 825-1709. mre2@psu.edu.

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