Few things bring more joy to a gardener’s heart than the sight of plump red tomatoes on the vine.
Nothing can harsh that buzz faster than those same tomatoes discoloring, forming deep cracks in the skin or simply rotting on the vine.
Tomatoes are vulnerable to a host of fungal, bacterial and physiological diseases. With this summer’s near record rainfall and humidity, conditions were just about perfect for everything from blight to rot.
The damage is not just cosmetic. Food safety experts in Maine warn the diseases — and even frost exposure — render the tomatoes unsafe to eat or process.
Anthracnose
This fungal disease is most evident when the tomato is at its ripest point. The first indication is small, circular depressions on the skin of the tomato that can expand up to nearly a half-inch in diameter. Sometimes they crack open exposing the tomato’s flesh.
The damper the conditions, the happier the anthracnose fungi. They need heavy moisture to reproduce and take hold. That’s why any tomatoes near the soil surface where it tends to be the most damp are most at risk. The fungal spores are also spread by splashing rain or water.
Early blight
This fungal disease also grows best in wet conditions and infects virtually every part of the tomato plant — stems, leaves and the fruit. The spores of the fungus are common here and very fast acting, according to the experts at University of Maine Cooperative Extension. Under optimal conditions they can germinate in less than 30 minutes and make their way into the tomato plant in as little as three hours. Once there, they wait for extended periods of wetness to spread their infection.
Rotting tomatoes are the most common sign of early blight. The disease starts off as small brownish spots and expands to a half-inch in diameter. Look for concentric rings in that darkened area which are the telltale signs of early blight rot. The area around the infection may start to turn yellow.
Blossom End Rot
End rot happens when there is a calcium deficiency in the plant. The blossom-end — the bottom — of the tomato becomes waterlogged and dies. The dead flesh can attract fungi or bacteria that rots the tomato, turning that area dark and mushy.
Dramatic changes in the amount of water a tomato plant receives over the season is one of the causes of end rot.
Cracking
You can also blame this summer’s wet weather for any cracking you see in your ripening tomatoes. Long periods of rain alternating with what dry conditions Maine did see this season causes the tomato fruit to have a growth spurt and skin can’t keep up with it. So it cracks as the tomato expands.
Toss those diseased tomatoes
The last thing anyone wants is to expose someone to food-borne illness. But that’s what can happen if you eat or serve diseased tomatoes. Even the healthy-looking parts of the fruit should be off the menu.
“Fruits and vegetables all have significant amounts of water in them,” said Kathy Savoie, professor with University of Maine Cooperative Extension. “That water is available to support pathogen growth.”
There are a whole host of pathogens that can enter a tomato through a diseased or damaged area. These include salmonella and other bacteria that can make you sick.
Once inside, they are free to reproduce and spread throughout the fruit.
“Both disease and frost exposure alter the state of the plant,” Savoie said. “You want to start out with high quality food you know is safe.”
Disease and frost exposure can also lower the acidity of tomatoes, Savoie said. Improper processing of tomatoes with low acidity can create conditions for the growth of deadly botulism, according to the United States Department of Agriculture.
“We advise people now to get out and get ahead of the frost and harvest what they can now,” Savoie said. “Then you can let green tomatoes ripen inside.”
Just check those ripening tomatoes often to make sure they are not rotting or decaying.
“From a food safety standpoint any rotted, decayed or blemished fruit is not of a high quality,” Savoie said. “Eating them is putting yourself in a high risk situation.”
