KJFM NEWS — Garden Talk is produced monthly at the Adair County University of Missouri Extension Center in Kirksville, Mo.

TOMATO FACTS, Physiological Disorders, AND Diseases

• American habits: According to the U.S. Department of Agriculture, Americans eat between 22- 24 pounds of tomatoes per person, per year. More than half of those munchies are ketchup and tomato sauce.
• Popularity: The tomato is America’s fourth most popular fresh-market vegetable behind potatoes, lettuce, and onions.
• Increasing popularity: Americans have increased their tomato consumption 30% over the last 20 years, mostly in processed forms such as sauce, paste, and salsa.
• How will you take your tomatoes? As of 2007, Americans spend more on salsa than tomato ketchup.
• Processed tomatoes: Americans consume three-fourths of their tomatoes in processed form.
• Largest producer: China is the largest producer of tomatoes, accounting for one quarter of the world’s production in 2009. The United States and India and the second and third highest producers respectively.

 

Tomatoes are good for you: Tomatoes are rich in lycopene, an antioxidant that is good for the heart and effective against certain cancers. Cooked tomatoes are actually better for you than raw ones, as more beneficial chemicals are released. Tomatoes are also packed with vitamins A and C, calcium, potassium.

 

The following are some problems you may see on tomato plants.

Early Blight is caused by the fungus Alternaria solani. It survives in infected leaf or stem tissues on or in the soil.  The first symptoms usually appear on the older, lower leaves of the plant and consist of small, irregular, dark brown to black, dead spots ranging in size from a pinpoint to 1/2 inch in diameter. As the spots enlarge, concentric rings may form as a result of irregular growth patterns by the organism in the leaf tissue. This gives the lesion a characteristic “target-spot” or “bull’s eye” appearance. There is often a narrow, yellow halo around each spot and lesions are usually bordered by veins. When spots are numerous, they may grow together, causing infected leaves to turn yellow and die. If not controlled, the leaves dry up and drop from the plant as the disease progresses up the main stem.  Recommended practices include mulching plants with straw, rotation, and the use of fungicides.  Daconil, Maneb, and Mancozeb are recommended for control, or any product containing Chlorothalonil.  Bravo is available for use by commercial growers. Always read the label directions before applying any pesticide.

Septoria Leaf Spot: Numerous, small, water-soaked spots, which are the first noticeable characteristic of Septoria leaf spot, appear on the lower leaves after fruit set. Spots enlarge to a uniform size of approximately 1/16 to 1/4 inch in diameter. They have dark brown borders and tan or light-colored centers. Yellow haloes often surround the spots. Severely infected leaves die and drop off. Septoria leaf spot is easily distinguished from early blight, another foliar disease of tomato, by the uniform, small size of the spots and the lack of concentric rings in the spots; however, Septoria leaf spot is sometimes confused with bacterial spot of tomato. The presence of fruiting bodies of the fungus, visible as tiny black specks in the centers of the spots, confirms Septoria leaf spot.  Control weeds in and around the edge of the garden. Rotate tomatoes with cereals, corn, or legumes. A 4-year rotation is recommended where disease has been severe. Apply fungicides on a preventative schedule. Fungicides containing chlorothalonil such as Daconil and Maneb are recommended for the homeowner.

Cracking is a physiological disorder caused by wide fluctuations in soil moisture. Tomatoes often start to crack during warm, rainy periods, especially if this weather comes after a dry spell. The tomatoes expand too fast and are most likely to crack when they have reached full size and are beginning to turn color. Some resistant varieties include Early Girl and Jet Star. Apply adequate moisture throughout the growing season to avoid the problem.

Catfacing is another physiological disorder of tomatoes. Tomatoes develop unusual swelling and streaks of scar tissue. It is caused by abnormal development of the tomato flower at blossom time. Cold weather at blossom set intensifies the deformities. Catfacing is not a disease. It is most common in the large-fruited beefsteak type tomatoes.

Blossom-end rot is a disorder that occurs on the bottom or blossom end of the fruit.  It appears as a sunken, water-soaked spot.  The spot turns brown or black, and dry and leathery as it grows larger.  It is not an infectious disease.  It affects both green and ripe tomatoes and is caused by a calcium deficiency, which is usually the result of wide fluctuations in soil moisture.  Keep tomato plants well-watered so they can take up the calcium from the soil.

Sunscald develops when high temperatures retard the development of good color.  Tomato fruits exposed directly to the hot sun may scald.  Sunscald is localized damage to the tissue often accompanied by discoloration.  Good foliage cover is helpful in preventing scalding.

Heat Stresses: Yellow Shoulder is caused from high temperatures and causes the shoulder or top of the tomato to turn yellow.  Hard white cores in tomatoes are also a heat stress disorder. Keep plants well-watered.