Thursday, July 22, 2010

Tomato talk (Darke County Extension Office)

After attending a church picnic this weekend and hearing all the latest garden gossip, this week’s column is about tomatoes. “Mr. Extension Educator, my tomatoes are dying. What is wrong?” That seems to be a common question these days. My response to that question every single time is, “how are they dying?” There are many diseases and nutrient deficiencies that affect tomatoes, and many of these can also affect other fruits and vegetables in the garden. It is important to know what disease you have and where it came from, so you can stop it!

I’ll work through some questions and answers that usually help us diagnose the problem. First of all, which part of the plant is dying, vegetative structure or fruit? This usually leads to a discussion of what constitutes what. The vegetative parts of a plant are the stems, leaves and roots, most of the time. Take potatoes for instance, the “vegetable” is actually a tuber, which is a structure of the root. On tomato plants, the fruit is what we commonly refer to as the tomato. Then we inevitably end up with, “is it a fruit or vegetable?” Now that depends on who you ask. The botanist, and being one I think of it as my favorite profession, will tell you the tomato by definition is a fruit, a berry at that. A politician will cite a Supreme Court ruling in 1893 that defined a tomato as a vegetable by its common use as something served with dinner and not dessert. Of course that was a matter of taxation, so they ruled to include tomatoes in a group that had higher tariffs. Anyway, I digress.

“My tomato fruit is dying.” Is it dying from the top or the bottom? “The bottom.” If we haven’t had severe heat or cold stress and the fruit is not sitting on the ground, then it is likely blossom end rot. This condition is actually caused by a calcium deficiency. It is easily solved by finding a fertilizer with calcium. This is another reason to have your garden soil tested. For proper sampling techniques, give me a call and I’ll come show you. This is especially important since the same condition occurs on peppers and eggplant.

If your fruit is dying and the entire berry is covered in sunken areas the size of a dime or even a quarter, you might just have anthracnose of tomato. The sunken areas will eventually turn black in the center. This one isn’t too common, but can occur in warm, wet weather. Anthracnose is caused by a fungus that also impacts peppers. If you do happen to see this one, act fast and find yourself a fungicide with anthracnose control in the label.

Now if the vegetative plant parts are dying from the bottom up you have two choices. If the leaves turn yellow and then die, there is a good chance you have Fusarium wilt. If the stems and leaves are covered in black lesions and spots, your tomatoes have early blight. Depending on when blight attacks, it can also cause flower drop and dark rot of the top of the tomato fruit where the stem attaches. Both of these are fungal diseases. Fusarium wilt generally impacts tomatoes, potatoes, eggplant and peppers, while early blight usually impacts tomatoes and potatoes.

You may have noticed tomatoes, potatoes, peppers and eggplants share many diseases. All of the above are in the family solanaceae, also known as the nightshades. Knowing about a plants natural history can help you manage your garden. I’ll give you a few integrated pest management tips to prevent disease. Number one is to properly fertilize and water your garden. Water at the base of the plant in the morning to avoid plants staying wet over night. A wet plant at night is a prime candidate for fungi to take hold. Rotate your garden so no nightshades are on the same plot that a nightshade was previously. If you do have a diseased plant, treat it with fungicide if the disease is caused by a fungus. When the diseased plant dies, hopefully of old age, remove it and all of its leaf litter from the garden. If you have any questions, or are having a disease outbreak, contact me at OSU Extension, Darke County, at 937-548-5215 or

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