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Some tomatoes grown to resist disease
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The tomato is the most commonly-grown vegetable in America’s backyard gardens. Unfortunately, producing big, red, juicy tomatoes requires considerable effort in preventing and controlling diseases.

The old adage “the best offense is a good defense” certainly rings true in the plant world.  By selecting tomato varieties that are disease resistant, you may be able to control certain diseases before they start.

The letters behind a variety’s name tell what diseases it is resistant to:

  • V: Verticillium Wilt
  • F: Fusarium Wilt
  • N: Nematodes

Some good possibilities are celebrity, carnival and better bush, but there are many others. Resistance does not mean the plants are immune to these diseases.

I have only positively identified verticilium wilt a few times over my 13 year career as an extension agent.  However, I have seen fusarium wilt on several occasions.

Fusarium wilt clogs the water conducting tissues in the tomato plant. The leaves yellow and wilt, often starting at the bottom of the plant. This disease can affect just one side or one to several branches of the plant. The plant can die early producing no fruit.

Control Fusarium wilt by planting resistant varieties. The “F” after the name, like celebrity VFN identifies these. Fusarium wilt can survive in the soil. Do not plant tomatoes in infected areas more than once every four years.

Bacterial wilt causes a rapid wilting and death of the plant. The plant dies so quickly it does not have time to yellow. To identify bacterial wilt, cut through the stem. Bacterial wilt browns the pith, or middle, of the stem. On bad infections, the pith may be hollow.

To determine if your plants are affected, cut a short section of the stem and suspend it in a clear glass of water. You can often see a “milky ooze” streaming out of the bottom of the cut stem.

There are no controls or resistant varieties for bacterial wilt. It also attacks peppers, potatoes and eggplant. Carefully dig out infected plants and soil and discard. Do not plant any of these vegetables in this area for at least four years.

Another common disease of tomatoes is early blight.  Most tomato gardeners have seen the symptoms: lower leaves turn bright yellow then drop off the plant. As the season progresses, most leaves may drop off the tomato vines, leading to sunscald of the fruit.

The fungus that causes early blight is present in most soils and can not be eliminated. The best practice to limit the disease occurrence is to mulch under the plant immediately after planting. This will prevent infected soil from splashing onto lower leaves.

Southern blight is a white mold that rots the stem at or near the soil line. The plant then wilts or dies. Look for the cottony fungus growth and the light brown BB-sized fruiting structures of the fungus. The fungus may be slightly above or below the soil line.

Bury all plant residues before planting and plant vegetables farther apart. Some gardeners wrap the stem near the soil line with foil to slow this disease and to control cutworms. The foil must extend two inches above and below the soil line.

For more information or to research tomato varieties, visit www.totallytomato.com.

Billy Skaggs is an agricultural agent and Hall County extension coordinator. Phone: 770-531-6988. Fax: 770-531-3994.