You don’t have to be an expert gardener to recognize that it’s a bad sign to find your tomato plant wilting. The downward drooping leaves are certainly an indication that something is wrong.
When you see a tomato plant wilting, you’re left wondering:
Is it just thirsty or does it have a disease?
In some cases, you just need to adjust your watering schedule and your plant will be fine. But sometimes, wilting is a symptom of infectious disease that can ruin your entire crop. There are some clues that can help you distinguish between them, and in this post, I’m going to go over the causes of tomato wilt and what you need to do to help your plant recover.
What causes tomato plant wilting?
Tomato wilt is a symptom of dis-ease that makes the tomato plant leaves droop and lose their shape. Wilting is most commonly a sign that your plants need water, and all plants will respond this way to dehydration. If the soil is dry and your plant is droopy with flat, thin leaves, you probably just need to water it. It should recover, but if it got too dry or this happens very often, don’t expect a good crop off of that plant.
On the flip side, too much water can cause wilting of plants. In this case, the soil around the plant will be wet and the leaves will droop but stay hydrated. Let the plant dry out and watch it for the next couple of days to see how it does. Don’t water again until the top inch of soil is dry. Container plants will also need some fertilizer as nutrients were likely washed out with the overwatering.
Watering tomato plants is a balancing act. Tomatoes need even moisture, and they don’t respond well to periods of dry or soggy soil. Water stress can lead to problems like tasteless fruit, blossom end rot, and cracking and even facilitate the spread of disease.
Other environmental causes of wilt in tomato plants
Tomatoes that experience a frost will wilt and not recover. The freezing of the water in their cells causes them to burst thus killing the plant. Also, certain trees like the black walnut, will stunt the growth and cause wilting of many plants including tomatoes. It is recommended not to plant under or near a walnut tree. If you’re looking at your wilted plant and there’s not an environmental issue causing wilt, then you might be dealing with one of the infectious causes of wilt.
Infectious causes of tomato wilt
When experienced gardeners and farmers talk about wilt, they are often talking about an infectious disease. Tomato wilt can be caused by many types of viral, bacterial, and fungal infections that can infect and destroy your entire crop. That’s why it’s very important to determine whether your plant is having a physiological response to stress or it’s come down with a sickness and you need to get it out of your garden asap.
There are several common causes of infectious wilt:
Tomato spotted wilt virus
Tomato spotted wilt virus is an infection that is can be seen worldwide. This viral infection is transmitted by several species of thrips which are tiny biting insects that find hosts on tomatoes and many other plants.
TSWV is not a disease of just tomatoes, but can also be found on peppers, potatoes, and several other flower and weed species. Symptoms vary by strain of virus, species of plant infected, and age of plant infected.
On tomatoes, symptoms usually appear on the youngest/growing portions of the plant. While signs of infection vary on a case by case basis, plants usually exhibit one or more of the following symptoms:
- Leaves turn a brown/bronze color and may curl upward
- Leaves can get clusters of small black spots
- Wilting and death of the growing portions of the plant.
- Both green and ripe fruit are lumpy with ring-shaped marks
Unfortunately, there is no way to treat infection with TSWV and infected plants should be culled and burned or tossed into the trash. You can send your plant for testing at your local university extension service if you want a firm diagnosis.
To prevent the spread, you really need to focus on getting rid of the thrips. If I knew they were spreading TSWV, I would skip all the horticultural oils and treat instead with either PyGanic or Naturalyte. Both of which are organic approved pesticides.
My preference is for Naturalyte because the active ingredient, spinosad, has no residual effect on pollinators, but PyGanic is a sure bet to get rid of your pest problem. In either case, avoid spraying when bees and other pollinators are active.
Fusarium wilt is a fungal infection common in areas with warm, moist weather. The fungus lives in the soil and enters the plants via their root system.
As it spreads, it grows up the inside of the tomato plant to the stem and branches via the vascular system. This clogging of its vascular system is what causes the symptoms of wilting and stunted growth. You’ll first notice the lower leaves turn yellow and start to die. Sometimes only one side or branch is affected at first, but eventually infected plants die.
This fungal disease is persistent in the soil indefinitely so the only recourse is planting resistant plants (indicated by the letter F after the name) or growing in new/sterilized containers and potting soil. Do not compost – destroy infected plants.
Verticillium wilt is very similar to fusarium wilt, but is more common in the north and favors cool moist soils. Verticillium wilt does not kill tomato plants but rather causes a drastic decrease in vigor and production.
Symptoms appear later in the season and include yellow discoloration of the older (lower) leaves of the plant. On the leaf, yellowing often begins in a v-shape and eventually extends to the whole leaf. The plant will wilt during the day but recover at night. Fruit may set but are smaller and fewer in numbers.
Both Fusarium and Verticillium will be evident if you cut open the stem of affected plants. You’ll see a brown to black discoloration of the vascular system whereas a healthy stem is only shades of green.
While there are ways to tell the difference, it can be very difficult to distinguish between verticillium and fusarium wilt in the field. So if you want to know which your property is affected with, you’ll need to send your plants to your local university extension office.
Like Fusarium, once verticillium is established in the soil, it will remain indefinitely. There is no way to treat or prevent infection so the only course of action is to plant resistant varieties (look for resistance label V) or plant in new containers and soil. Don’t compost – destroy infected plants
Caused by the bacterium Ralstonia (Pseudomonas) solanacearum, bacterial wilt works in the same way as the fungal wilts. The bacteria grow in and lead to the death of tomato plants. This bacteria thrives in hot and wet soils and once established remains infective for many years.
Bacterial wilt can be distinguished from other forms of wilt at home. Compared to the fungal wilts, bacterial wilt causes wilting of the youngest (uppermost) leaves. Leaves do not turn yellow but rather stay green. When you cut the stem of tomato plants infected with bacterial wilt, you’ll see a white milky substance instead of the brown growth of the fungi.
When freshly cut stems are placed in a glass of water, you can see the white substance draining from inside. If you notice these symptoms and suspect your plant is infected with bacterial wilt, pull it out of the garden right away and dispose of it. Don’t compost – destroy infected plants.
The only method of control for bacterial wilt is planting resistant varieties or grafted plants on resistant rootstock. There is no treatment for infected plants or soil. If you confirm the presence of bacterial wilt in your garden, you’ll do better to plant tomatoes in containers from now on.
Root knot Nematodes
Nematodes are tiny wormlike creatures that infest and feed on tomato roots. Their presence causes knots or galls of the roots and damages their ability to take up food and water. Symptoms of root knot nematodes include wilting, stunted growth, and pale color. You’ll also see the knots or galls on the roots of the plants.
You can find tomato varieties that are resistant to nematodes as indicated by the letter ‘N’ after the variety name. Nematode numbers can be decreased by growing resistant varieties for several seasons. However, when susceptible varieties are then planted, numbers of nematodes will rise again.
Also affects pepper, cucumber, squash, eggplant, and okra.
Another fungal disease, southern blight causes sudden wilting and death of the entire plant. Also known as Southern Wilt and Southern Stem Rot, the fungus enters the stem at the soil line causing the plant to suddenly wilt and die. Infection leaves a telltale dry brown rotten spot around the base of the stem which may develop a white moldy growth in high moisture situations.
The fungus lives in the top 2-3 inches of soil and high temps and wet, acidic soils encourage growth. Once the fungus is established in the soil, it can be hard to get rid of it. Grow tomatoes in raised beds or containers or grow nonsusceptible crops (corn and cover crops) for a minimum of 2 years before planting tomatoes in that area again.
Dealing with tomato wilt
Beyond optimizing your watering schedule, the best recourse for dealing with tomato wilt is to plant resistant varieties. Look for resistance label VFN, and keep in mind that many resistant tomatoes are hybrids…and it’s okay to grow hybrids even in an organic garden.
Some of my favorite wilt-resistant tomatoes are:
- Big Beef
But there are several options for you to look through at Johnny’s seed supply.
Have you lost tomato plants to tomato wilt disease?
Tell us about your experience in the comments below.
This post was updated on 12/24/22 to improve format