This Saturday, July 27, is the annual celebration of the Tomato Festival at the Downtown Cartersville Farmer’s Market. Activities will begin around 10am and will include a tomato contest for local farmers. The festival has become a favorite event among locals that love to sample different tomato varieties. There are literally thousands of tomato varieties grown around the world. Rutgers University maintains an extensive online database of tomato variety descriptions and pictures if you’re interested in learning more. Their database organizes tomato varieties by 20 different shape categories and several skin colors, including bi-color, black, pink, green, golden, orange, purple, red, white, and yellow.
As in previous years, the Farmer’s Market will have samples of locally grown tomatoes that the public can taste and cast ballots to decide who will win the coveted “best tasting tomato” award. There are also additional categories that the public can judge based on appearance for “Prettiest Tomato”, “Ugliest Tomato”, and “Biggest Tomato.” My favorite category is the “Ugliest Tomato” award, which often generates questions about why do they look that way? In fact, this is a common question we get at the local Extension office this time of year.
There are several tomato disorders that cause a variety of “ugly” deformities in tomatoes. Most of these disorders are caused by environmental stresses and sometimes insects or certain plant diseases. In most cases, the tomatoes may look bad, but are still edible as long as the fruit are harvested before they start to rot. Many fruit rots are caused by decaying fungi and bacteria that will take advantage of deformed tomatoes, which ultimately shortens the shelf life of the fruit. In most cases, it’s best to harvest ugly tomatoes slightly on the green side before they get real ugly and turn sour. Small blemishes can be cut out with a knife in order to salvage a few pieces for a fresh tomato sandwich. If you’re going to use them for salsa or spaghetti sauce, then appearances aren’t that important anyway.
One of the most common disorders of tomatoes is blossom-end rot, which causes the bottom of the fruit to turn black and leathery. This particular issue is caused by a calcium deficiency and can often be avoided by adjusting the soil pH of your garden based on a soil test. Changing the soil pH with limestone takes time and should be started several months prior to planting tomatoes.
Another common problem on tomatoes is called growth cracks or rain check. These can form circular patterns that crack and split around the stem scar or radial cracks that split outward from the center stem. Some varieties of tomatoes are more prone to growth cracks than others. Take note of those varieties that are most affected and consider avoiding those in the future. Rapidly growing fruit, especially on plants that receive high amounts of nitrogen fertilizer are more susceptible to cracking. Wide fluctuations in rain and temperature can also cause fruit to crack more readily.
Tomatoes affected with “catfacing” or “zippering” have thin, brown scars that start at the stem and extend part or all of the way to the blossom end of the fruit. These long scars resemble a zipper pattern and usually have only one scar per fruit. These disorders are thought to be caused by flowers sticking together or flower anthers that remain attached to the ovary wall of newly forming fruit and is more common during cool weather. Certain varieties are more susceptible than others.
Stinkbugs and leaf-footed bugs are sap-sucking insects that commonly feed on the fruit of tomatoes. The damage from these insects appears as small, yellow pinpricks surrounded by white corky tissue under the skin. Sometimes, the fruit becomes deformed as it enlarges after this type of insect feeding injury.
Tomato spotted wilt virus is a common problem that causes the fruit to develop mosaic ring spots. On ripe fruit, these turn into obvious ring patterns, which become red and yellow. The only way to avoid this virus is to control the insect vector that spreads this disease, known as thrips. There are several virus resistant tomato varieties on the market today. For more information, check out our free UGA Extension publication on “Troubleshooting Cultural Problems of Tomatoes” on our website at https://t.uga.edu/57n.
Paul Pugliese is the Extension Coordinator and Agricultural & Natural Resources Agent for Bartow County Cooperative Extension, a partnership of The University of Georgia, The U.S. Department of Agriculture, and Bartow County. For more information and free farm, lawn, or garden publications, call (770) 387-5142 or visit our local website at ugaextension.org/bartow.