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Diseased tomatoes

*This is an excerpt from The Alabama Vegetable Gardener, ANR-0479.

Tomatoes are by far the favorite and most widely grown vegetable in home gardens. Nothing can be more satisfying than picking a juicy red tomato from your own garden on a hot summer day for a salad or a sandwich. To have a plentiful supply of top-quality tomatoes throughout the summer, you must not only fertilize tomatoes correctly but control diseases as well.

Unfortunately, few gardeners realize the need to control diseases. As a result, they harvest progressively poorer quality fruit over a much shorter period than they could have from healthy plants. Actually, most garden varieties of tomatoes can produce until frost. This means that gardeners in South and Central Alabama could enjoy fresh tomatoes well into November and even December in many years.

Tomato diseases can be successfully controlled with a little extra effort and planning before setting out plants. The first step in planning a successful disease control program is to select a location for your tomatoes that has good drainage and is in a full-sun location. It is best to select a site that has not had tomatoes, peppers, or potatoes grown on it within the past 2 years. This practice will reduce the risk of soilborne diseases such as Fusarium wilt, seedling diseases, or nematodes. When purchasing tomato plants, examine them carefully for leafspots or signs of injury on the stems. Buy only those plants that have a healthy green appearance and are free of blemishes. Be sure to select varieties that are resistant to some of the more common diseases such as Fusarium wilt, Root-knot nematode, Verticillium wilt, and Tomato Spotted Wilt virus. This information should be listed on the seed pack or label. For example, varieties that have the letters V, F, & N near their name are resistant to Verticillium, Fusarium, and Root-knot nematodes.

When handling tomato plants, make certain you have washed your hands thoroughly, particularly if you smoke or chew tobacco. Tobacco Mosaic virus, a destructive disease on tomatoes, can be transmitted to tomatoes by tobacco contaminated hands.

Once the plants are in the ground, you should begin a regular disease control spray program within 7 to 10 days. Proper equipment, spray coverage, and timing are critical to control foliar diseases. You should have a 2- or 3-gallon stainless steel or noncorrosive sprayer that can produce a fine spray. All parts of the tomato plant must be sprayed. Spray fungicide at 7- to 10- day intervals throughout the growing season.

There are fungicides available that do an excellent job of controlling early blight, the predominant foliar diseases in Alabama. Mancozeb, chlorothalonil, and liquid copper fungicides are frequently used and control a variety of foliar fungal diseases. Occasionally, bacterial leaf spot becomes a problem. When this happens, copper must be added to the spray mixture since fungicides will not control bacterial diseases. Later in the season when insects such as tomato fruitworm become a problem, insecticides can be added to the fungicide spray mixture.

When using any pesticides, read the labels carefully and follow their directions. Some fungicides and insecticides have restrictions concerning the time of their last application and harvest. Be sure to heed these restrictions; always follow proper procedures.

Beautiful homegrown tomatoes require a lot of work and a good disease control program, but the extra quality and season-long enjoyment of such a fruit is well worth the extra effort.


For more information, see other excerpts from The Alabama Vegetable Gardener, ANR-0479.


Kerry Smith, Extension Home Horticulture Associate; Ayanava Majumdar, Extension Entomologist; Charles Mitchell, Extension Agronomist, Professor, Agronomy and Soils; John Everest, Visiting Professor, Agronomy and Soils; Edward Sikora, Extension Plant Pathologist, Professor, Entomology and Plant Pathology; Joseph Kemble, Extension Specialist, Professor, Horticulture; all with Auburn University; and Rufina Ward, Research Entomologist, Natural Resources and Environmental Sciences, Alabama A&M University.

Reviewed October 2021, The Alabama Vegetable Gardener, ANR-0479

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