What Is Bacterial Wilt Of Tomato? (Plus 7 Resistant Varieties)


Bacterial Wilt is one disease that can really hurt your tomato plants and reduce your yield at harvest.  Fortunately, there are ways to prevent the disease and choose plants that will resist it.

So, what is bacterial wilt of tomato?  Bacterial Wilt of tomato is a disease caused by the bacterium Ralstonia Solanacearum.  It can infect plants by damaged roots or by carriers such as nematodes.  The disease thrives in moist soil and in temperatures over 85 degrees Fahrenheit (30 degrees Celsius).  A few leaves on top of the plant wilt first, then the entire plant wilts, and finally the stem will turn brown.

Of course, there are plenty of ways to prevent this disease, although there is no cure.

In this article, we’ll talk about what causes Bacterial Wilt, what its symptoms look like in tomato plants, and how to prevent the disease.  We’ll also look at some tomato varieties that are resistant to Bacterial Wilt.

Let’s begin.

What Causes Tomato Bacterial Wilt?

According to Clemson University, the bacterium Ralstonia Solanacearum causes tomato bacterial wilt.  The bacteria can infect a tomato plant in a few ways:

  • Through damaged roots – when roots are damaged during transplant, or when new roots emerge from the stem, the bacteria can get into a tomato plant.
  • In Soil – if the disease already existed in the soil from prior years, it can infect newly planted tomatoes.
  • From Carriers – root-knot nematodes and other insects can carry the disease and spread it by introducing it to tomato plants.
root knot nematode
Root-knot nematodes can carry and transmit bacteria that causes Bacterial Wilt in tomato plants.

The disease is develops faster moist soil and in temperatures above 85 degrees Fahrenheit (30 degrees Celsius).  It is common in the Southeastern U.S.

According to the North Carolina State University Extension, other plants can get Bacterial Wilt as well.  This includes members of the Solanaceae (nightshade) family and others, such as:

  • Eggplants
  • Peppers
  • Potatoes
  • Sunflower
  • Dahlia
  • Geranium
  • Marigold
  • Zinnia
potato plants in container
Potato plants can also get bacterial wilt, so don’t plant them to close to tomatoes.

To prevent the spread of Bacterial Wilt, wait at least 3 years before planting any of these in the same spot where tomatoes were planted.

What Does Tomato Bacterial Wilt Look Like?

Tomato Bacterial Wilt affects mature plants with fruit in mid-season (midsummer).   The bacteria infect the vascular system and multiply until the plant’s vessels are clogged.

After becoming clogged, these vessels will no longer be able to carry water and nutrients to the plant’s tissues.  Eventually, a plant will succumb to the disease.

dying tomato plant
The leaves on a tomato plant wilt, but stay green, when infected with Bacterial Wilt.

Here are the symptoms of tomato bacterial wilt:

  • A few leaves wilt – the youngest leaves (on top of the plant) wilt first.  The leaves at the ends of branches wilt sooner that those closest to the plant.  The plant and its leaves are still green at this stage, so it may be hard to diagnose the disease.
  • The entire plant wilts – eventually, the entire plant wilts, including all of its leaves.  This may appear to happen suddenly.  At first, the plant may look wilted in the afternoon, look better in the morning, and then wilt again in the afternoon, despite any watering efforts.  The leaves may become dry, but remain green.
  • Brown discoloration (cankers) of stems and leaves, along with root rot – this starts at the base of the plant.
  • Stunted growth – infected plants may also have slow growth or reach a limited height.

These symptoms appear and progress faster in temperatures of 86 to 95 degrees Fahrenheit (30 to 35 degrees Celsius).

Identifying Bacterial Wilt Of Tomato

According to Clemson University, there is a way to test a diseased plant for Bacterial Wilt:

  • First, cut a piece of the stem at the base of the plant.
  • Next, if the stem tissue is discolored, rinse it and put it in a glass of water.
  • Now, wait 5 minutes.  If the tomato plant had Bacterial Wilt, a white substance will appear in the water.

It is easy to confuse Bacterial Wilt of tomato with other diseases that affect tomatoes.  Here is how to tell them apart:

  • Blight – a plant infected with blight wilts.  However, you will also see white strands (fungus) growing up the stem, starting at ground level.  This disease starts at the bottom of the plant.
  • Fusarium Wilt – on a plant infected with Fusarium Wilt, the leaves on one side of a branch wilt or turn yellow.  This disease starts at the bottom of the plant.
  • Verticillium Wilt – on a plant infected with Verticillium Wilt, you will see V-shaped yellow or brown lesions on leaves.  This disease starts at the bottom of the plant.
tomato early blight
Tomato blight, pictured here, starts at the bottom of plants. Bacterial Wilt starts at the top of plants.

All of these diseases start at the bottom of the plant.  Bacterial Wilt of tomato starts at the top of the plant.

How To Treat Bacterial Wilt In Tomato Plants

According to the North Carolina State University Extension, there is no way to treat a plant infected with tomato bacterial wilt.

However, you can take steps to limit the introduction and spread of the disease in your garden.

How To Control Bacterial Wilt Of Tomato

When infected tomato plants die, their roots and stems release the bacteria into the soil.  Running water can spread the disease to other parts of the garden.

Moving soil (with a shovel or rake) can also move the disease around in the garden.  In addition, pests can carry and spread the disease to different plants in your garden.

You can find some organic pest control methods in my article here.

Here are some preventative measures to help with tomato Bacterial Wilt management:

  • Buy healthy transplants – infected transplants grow into infected mature plants, which can spread the disease to other plants and into your soil.
  • Build raised beds – this improves drainage and prevents the moist soil conditions that allow Bacterial Wilt to thrive.
  • Irrigate with clean water – avoid using water that may contain bacteria from other plants.
  • Protect plants from pests – use a clear plastic cloche to protect young tomato plants from cold and pests.  For more mature plants, you can use row covers to protect against pests.  A row cover also provides cold protection later in the season.
  • Prevent growth of weeds – some weeds can also carry and spread Bacterial Wilt.  Use mulch to smother existing weeds and to stop new weeds from growing near tomato plants.
  • Remove infected plants – this stops the disease from spreading into the soil or to other nearby plants.
  • Use crop rotation – avoid planting tomatoes in the same spot every year.  A good crop rotation schedule is to plant tomatoes in the same spot only once every 4 years.  You can learn more about good crops to rotate with tomatoes in my article here.
  • Dig or till carefully – don’t dig or till infected parts of the garden until last.  Then, clean your equipment with alcohol to prevent the disease from spreading.  According to the University of Florida, Bacterial Wilt can survive for years in soil or plant debris, even in cold temperatures.
wooden raised garden beds
Use raised beds to improve drainage and avoid conditions that cause Bacterial Wilt.

7 Varieties Of Tomatoes Resistant To Bacterial Wilt

There are two ways to get tomato plants that are more likely to resist Bacterial Wilt:

  • 1.) Grow tomato varieties that are resistant to Bacterial Wilt
  • 2.) Graft a scion onto a tomato rootstock that is resistant to Bacterial Wilt.

We’ll take a look at both methods below.

Planting Tomatoes Resistant To Bacterial Wilt

There are a few tomato varieties that have at least partial resistance to Bacterial Wilt, including:

  • Florida 7514 – this red tomato variety is determinate, heat tolerant, and matures in 75 days.  It is resistant to bacterial wilt, as well as Bacterial Speck, Fusarium Wilt, and Verticillium Wilt.  You can find Florida 7514 tomatoes from Jung Seed.
  • Neptune – this red tomato variety is determinate and matures early in the season.  It is resistant to bacterial wilt and tolerates heat.  You can find Neptune Tomatoes from Heritage Seed Market.
  • Tropic Boy – this red hybrid tomato variety is indeterminate and tropical.  The fruits are large with tough skin and firm flesh, maturing in 85 days.  It is resistant to Bacterial Wilt, as well as Fusarium Wilt and nematodes.  You can find Tropic Boy tomatoes from seedman.com.

If you combine these varieties with the preventative measures listed earlier, you will have much better results.  Of course, you also have the option of grafting tomato plants.

Grafting Tomato Plants (Rootstocks Resistant To Bacterial Wilt)

You can also use a rootstock that is resistant to Bacterial Wilt and graft it with a different scion to increase resistance.  Some Bacterial Wilt resistant tomato varieties you can use as rootstock include:

grafted tomato plant
Here is a grafted tomato plant.
Image courtesy of: Caryrivard via Wikimedia Commons https://commons.wikimedia.org/wiki/File:Tomato_graft_union.jpg

Note: these varieties should only be used as rootstock for grafting.

If allowed to grow on their own without a grafted scion, the plants will often produce fruit that is not good for eating (they are bred for disease resistance, not for producing good fruit!)

You can learn more about grafting tomato plants in this article from the Purdue University Extension.

Conclusion

Now you know what Bacterial Wilt is and how to prevent it.  You also have some options for growing plants that will resist the disease, possibly by grafting.

If you aren’t convinced that your tomato plants have Bacterial Wilt, you can find some other causes of curled leaves on tomato plants in my article here.

I hope you found this article helpful.  If so, please share it with someone who can use the information.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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