This article originally ran in the Ruston Daily Leader on April 20, 2010.

All tomatoes are acidic regardless of their color. Those said to be low acid are really normal or high in acidity but also are high in sugars which impart a sweet taste that masks the sharp acidity.

For instance, Buckeye rot, Blossom-end Rot, Early Blight, Leaf Spot, Fusarium Wilt, Tomato Spotted Wilt Virus, Bacterial Canker along with others have all been a challenge to the home gardener. Even with these problems the average home gardener can still grow tomatoes with some success.

Dealing with Pest Problems

By now most of you have your plants growing in the home garden or container garden and looking for fruit set. One of the most troublesome fruit problems is Blossom-end rot. Blossom-end rot is distinguished by a black round circle on the blossom end of the fruit, however do not panic. Blossom-end rot can easily be corrected. It is caused by a calcium deficiency and is aggravated by any kind of drought stress or extreme fluctuation in soil moisture and over fertilization, especially with nitrogen. The calcium content can be determined by a soil analysis. If calcium is low, the soil should be limed. Another practice that will help to reduce blossom-end rot is to try to keep the soil as uniformly moist as possible. Do not let the plants dry out before irrigating. Provide good drainage to remove excess water after a heavy rain, use mulch, and do not over fertilize. There are materials sold in local garden centers which can be sprayed onto the plant and corrected by the time the plant sets the next cluster of fruit.

As you await your first picking, you may suddenly find much of the fruit rotting after a period of heavy rainfall. Spores which cause Buckeye Rot are splashed from the soil onto the lower fruit cluster. Then they enter the fruit and may rot half of it rapidly. The rot may form regions with lighter and darker bands or rings in the fruit just under the skin. Buckeye Rot can be controlled only by spraying immediately after periods of heavy rainfall. A good mulch cover will help stop some of the splashing of mud.

Early Blight is a fungus disease problem that can affect both leaves and stems. The symptoms of the disease are brown spots on leaves or stems. These spots average about one-half inch in diameter, are irregular and may take on a concentric ring or “bullseye” pattern. Preventive fungicide sprays at regular intervals are necessary to control early blight.

Fusarium Wilt is the most common and destructive soil-borne disease in Louisiana. The disease is most severe during warm weather and enters the plant through the roots to develop inside the stem. The plants show a progressive yellowing and wilting starting at the bottom. A week or two may past between first symptoms and plant death. If the stem is cut near the soil line, a brownish discoloration can be seen in the inner tissue of the plant. The best control measure is to use disease-resistant plants. The presence of this resistance is often designated on a seed packet or plant label as “F” following the variety name. Many varieties will have resistance, but keep in mind that resistance does not imply immunity. Under stress conditions or in heavily infested soils, these resistant varieties may also develop disease. In severe cases, soil sterilization or a new planting site should be considered.

Southern Blight is another soil-borne wilt. It develops in warm weather and may quickly spread from plant to plant. A cottony fungus growth at the soil line may be observed with Southern Blight. Later stages, the fungus may develop mustard seed like ‘sclerotia’ on the stem near the soil line. Soil applied fungicides are recommended to control Southern Blight.

Bacterial Wilt is a serious disease in the southern United States. It is caused by a soil-borne bacterium. It is similar to Fusarium wilt in symptoms, except that it kills the plant quickly. If Bacterial Wilt is contracted, it will be necessary to rotate the tomatoes to a new planting site.

The Tomato Spotted Wilt Virus, also called curly top, can cause unusual symptoms to develop in the plant. The upper leaves and upper portion of the plants may curl, twist and become very stunted. The leaf veins often turn purplish in color and the leaves turn yellow. The virus is transmitted by insects called thrips. These insects should be controlled early with an insecticide. Immediately after diagnosing a plant as having Tomato Spotted Wilt Virus, it should be discarded and removed from the garden.

Do not be discouraged by the problems mentioned above you can still grow tremendous tomatoes. Consider planting disease-resistant varieties of plants as well as your favorite personal preferences. For instance, Amelia is a variety of tomato that has resistance to Tomato Spotted Wilt Virus and has an excellent flavor as well. Also worth trying are Roma tomato plants they are very tough and seem to produce tomatoes without the spraying of pesticides. A pesticide program of insecticide and fungicide is an excellent cultural practice to use as well.

Please contact me, if you have any questions or concerns regarding this topic and any other related topics.