If you’re growing tomatoes regardless if it’s in pots, a garden, or raised beds, one of the most common problems you’d encounter is tomato leaves curling. It’s one of the tomato diseases that you might experience.
In some cases, the leaf curl is nothing to be concerned about, however, there are a few cases that not only can kill your tomato plant but can also spread through your garden. Keep reading to find out what are those 3 causes and how to deal with them.
1. Physiological Cause
When I say “physiological”, that’s a fancy way to say environmental. The symptoms of physiological causes might include overwatering, underwatering, wind, dry weather, or heat. Your tomato plants would most likely experience this cause. It’s the most common one.
Symptoms:
Look out for the following signs of environmental causes in tomato leaves curl:
- The color of the leaves stays the same lush green (in other words, the tomato leaves won’t change color)
- The leaves generally get thicker, sort of leathery.
- The most obvious sign would be the tomato leaves curling inward
Why are my tomato leaves curling upward?
Even though it might look disturbing, this is not a bad thing. The reason behind tomato leaves curling upward or inward is usually the heat, dry wind, or dry weather. If the weather is too hot, the plant naturally roll-up its leaves upward to protect it from losing too much moisture.
Normally, when the leaves are open, there’s normal evaporation due to the heat. But if the heat is getting too high and the evaporation is too much, the tomato naturally protects itself by curling up the leaves to reduce or lower the evaporation that occurs. The less surface area there is for the sun to hit, the lower the evaporation is.
What to do if your tomato leaves are curling upwards?
If the temperature is not hot (over 90˚F or 32˚C), you can leave the plant alone. It’s nothing to worry about. However, if it’s too hot then what you can do is throw a shade cloth over the plant (30% or 50%). It could help with the leaf curling and protect the plant from dropping its flowers.
Keep an eye on the temperature and the tomato leave curling. If it’s too hot for quote prolonged period, not even the cloth would work.
Do not quickly grab a watering can to water the plant. In most cases, this might hurt the tomato plant more than being helpful. Always check whether or not the soil is moist. The usual way – stick a finger inside the soil and if it’s moist, the tomato doesn’t require watering.
What happens is that the tomato plant cannot pull enough water through the roots to compensate for the water loss of the leaves’ evaporation.
The bottom line is if it’s a short period of heat, it won’t affect the fruiting of the tomato or the growing.
2. Herbicide Drift
Herbicide drift is another reason for tomato leaves to curl. If you are using herbicide in your garden or live close to a place that uses herbicide, it could easily drift to your tomato plants and cause the leaves to curl.
Symptoms
The symptoms of a herbicide drift should include the following:
- The tomato leaves cup up
- The stem part of the tomato leaves bends down
- Possible discoloration of the leaves – yellow or brown color
Treatment
What you need to know is that the herbicide drift only affects the already existing leaves. This means that any new tomato leaves that grow after that should not have that problem. Of course, assuming the herbicide is gone.
3. Viral Cause
Out of the 3 causes, the vilar one is the most worrisome. The bad news is that if that happens, it’s quite impossible to turn around and the plant would (if it hasn’t already) die.
There are many different kinds of tomato viruses that could cause the plant’s leaves to curl. But the most common 3 are:
- The curly top virus
- The yellow tomato leaves – the mosaic virus
- The yellow curly leaf virus
The curly top virus
Symptoms
Out of those three, the curly top virus is the most common one. This one is commonly mistaken for the environmental one, as it shares the same curling upward as a symptom. However, the curly top virus might also point the whole leave upward. The symptomatic leaves might also develop purple veins.
If the tomato plant is infected early, it can be severely stunted.
How can you differentiate between the physiological vs curly top viral tomato leave curl?
Since the symptoms are quite similar, what you can do to check which cause is the reason for the leave curling is to wait for the evening, then water the tomato plant.
The following morning check on those tomato plants and see the condition of the leaves. If they’re back to normal, then the reason for the leave curling was physiological (i.e. the heat or dry wind/weather). If they’re not, you probably have the curly top viral issue.
Does the curly top viral spread through the other tomato plants?
When a tomato plant has a curly top virus, it doesn’t necessarily mean that it will spread through all of the other tomato plants that are nearby. Even if it’s slightly touching the other plants.
With that being said, you need to know that the virus can be spread due to the leafhopper bug. What happens is that if a leafhopper chewed on the infected tomato plant and then moved to chew on a non-infected plant, it can (and probably will) pass the infection.
Treatment
Simply put, if you notice that a tomato plant has the virus, the best thing you can do is to get rid of it. You don’t want to risk the leaf hoppers coming and infecting the rest of the tomato plants that you have.
I know it’s sometimes hard to kill a plant, but it’s better to remove this one tomato plant than all of them.
If you insist on trying to save the plant, you can attempt to move it to a shady place or use a shade cloth as mentioned above. The reason behind this is simple – the leaf hoppers like to eat in the sun, therefore they will avoid a tomato plant that’s in the shade.
The Tomato Mosaic Virus
Symptoms
In order to recognize this tomato virus, look for the following symptoms on the tomato plants and specifically, the leaves:
- Rolling of the leaf
- Change in color of the leaf – toward yellow or brown
- Small leaves
- Possible browning of the infected fruit
Treatment
Just like with the curly top viral, there’s no treatment for this one either. This s a virus that can live in the soil for up to 2 years.
Prevention
When watering your tomato plant, don’t let the water splash from the soil to the leaves as you can spread the mosaic virus that way. Make sure to water from below, near the base of the plant. In addition to that, add a layer of mulch if possible.
But if your tomato plant gets infected by this virus, the best thing you can do is to get rid of the plant instead of risking getting all your crops getting infected.
The Tomato Yellow Leaves Curl Virus (TYLCV)
Symptoms
The symptoms to watch out for when it comes to the tomato yellow leaves curl virus are:
- Leave cupping (either upward or downward)
- Yellow tomato leaves
- Significant reduction of leave size
- Flower drop
- Fruit drop
- Possible plant stunting
Treatment
Unfortunately, this is another one that cannot be treated. What you can do, however, is to grab a black shield or a plastic bag, wrap the entire plant in it, and right at the soil level near the truck, you want to tie it with a rope.
By covering the entire infected tomato plant, the white flies won’t have access to it and spread it to the rest of the plants in your garden or greenhouse.
Next, you want to grab it at the base and cut the whole plant. Leave it in the sun for maybe a few days to dry out but the main goal is to kill all the white flies in the plastic bag and contain most of the virus.
Once you have done all of that, make sure to start a neem scheduling after that.
Prevention
The white fly spread this virus and to keep the white flies in your garden under control spray with neem oil every other week.
Important!
If a tomato plant is infected by any of the viruses we’ve mentioned above, DO NOT put it in a compost bin. You should put it in the trash to avoid spreading the virus.
Verdict
As you can see, some of the reasons for a tomato leave curing are not that scary at all. They are expected and a natural reaction of the plant towards the environment.
The concerning part is the viruses. My personal advice is to always sacrifice a single plant if it got infected by any of the listed tomato viruses than risking the entire garden’s health.
