Wilt Can Sadden Tomato Lovers

— Written By and last updated by Diane Lynch

Q: Why is my tomato plant wilting?

A: Tomato wilt diseases probably rate high on the list of frustrations in the garden. Nothing is more frustrating than planting and caring for tomato plants with the anticipation of getting to enjoy the taste of a homegrown tomato, only to discover your plants wilting away just before the tomatoes are ready to harvest. There are a number of different tomato wilt diseases that are common each year in the garden and unfortunately are a tough battle to fight.

Verticillium and Fusarium wilts are two common diseases of tomatoes. Both of these diseases are caused by a fungus that is soil-borne and passes upward from the roots into the tomato stem blocking water from moving up the plant, thus causing it to wilt. The initial symptoms of these two diseases are wilting of the plant leaves during the heat of the day (often mistaken as lack of water) and then recover in the evening or overnight. Gradually, the wilting becomes worse and more often eventually resulting to the plant dying.

Bacterial wilt or Southern bacterial blight is a disease caused by a bacterium that survives in the soil. The disease is most active in a high temperature, high moisture environment. The bacteria enters through the roots where is multiplies rapidly inside the stem, filling it with slime which results in a rapid wilt of the plant while the leaves stay green. Occasionally, yellowish ooze can be visible when cutting open an infected stem.

Tomato spotted wilt virus is a disease that is spread by thrips. Thrips are tiny insects that pick up the virus when feeding on infected weeds and other plants, then spread it to growing tomato plants. Several weeks after transplanting tomato plants into the garden, some plants may appear stunted. Younger leaves may have bronze or dark spots or prominent purple veins. With time, upper foliage of infected plants become twisted and cupped. The virus can even possibly cause yellow or green spots or rings on the fruit. Younger tomato plants are more apt to wilt and die from tomato spotted wilt virus, however older plants can survive but bare discolored fruit that may not fully ripen.

When we talk about control, unfortunately the news is not good. Once a tomato plant shows symptoms of a wilt disease, it can not be cured of the problem. There is not any chemical control available for any of these tomato wilt diseases. Once tomato plants show symptoms of wilt disease, it should be pulled up and removed from the garden. Removing old and diseased plant debris during the growing season and at the end of the growing season won’t eliminate the problem next year but overtime can help reduce the population of the diseases that overwinters in the soil.

To battle tomato wilt diseases, it takes some careful planning at the beginning of the growing season when selecting varieties and deciding where in the garden to plant. When selecting what tomato varieties to grow, selecting ones that are resistant to a disease. Look for letters with variety names that serve as a code from which disease it is resistant to. Verticillium wilt resistance is represented by a “V”, while fusarium is “F”, and tomato spotted wilt virus is “TSWV.” You will find that some varieties have resistance to more than one disease while others may have no resistance. Do keep in mind that resistance means that the plant will be better able to survive through a particular disease but does not necessarily mean that the plant is completely immune to the disease.

Because verticillium, fusarium and bacterial wilt all survive in the soil for several years, it will be hard to prevent the disease each year. Crop rotation can help but is often of limited value due to limited garden space. If you experienced wilt problems this year, if at all possible, you will want to avoid planting tomatoes next year in that same spot. Along with not planting tomatoes in locations with a history of wilt diseases, you would also want to avoid planting other vegetables that are in the same family as tomatoes which includes peppers, eggplant, and potatoes. These vegetables are all closely related and can be infected by similar diseases. If wilt diseases become a continuous problem no matter where you plant them, you may have to consider planting in containers to avoid the infected soil all together.

For tomato spotted wilt virus, eliminating weeds in the garden is the first step in reducing the problem. Keep grass and weeds mowed in surrounding areas to reduce the spread of thrips onto tomato plants. Even weeds in the garden during winter can harbor thrips and the virus until the following growing season.

There is no doubt growing tomatoes can be challenging when you are dealing with one or more of the many disease problems that infect tomatoes. Careful planning at the beginning of the season by planting resistant varieties and avoid infected soil, can hopefully result in you getting to enjoy nice homegrown tomatoes in the future.

For additional lawn and garden information contact the Wayne County Extension Master Gardener Volunteer Plant Clinic on Mondays and Wednesdays from 10 a.m. to 1 p.m. The plant clinic is a free resource to Wayne County residents. One can reach the Wayne County Extension Master Gardener Volunteer Plant Clinic by phone at 919-731-1433, e-mail at Master.Gardener@waynegov.com, or stopping by Room 100 of the Wayne County Extension Office (208 West Chestnut Street, Goldsboro).

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Jessica Strickland
Extension Agent
North Carolina Cooperative Extension
Wayne County Center
P. O. Box 68
Goldsboro, NC 27533