There is nothing more satisfying than a good tomato crop for a gardener. But tomato leaf curl or leaf roll can replace your happiness with worries and uncertainty. This guide will help you figure out what exactly is a tomato leaf curl, what causes it, and how can you fix or undo it.
Let’s dive right into the nitty-gritty of tomato leaf curling, its different causes – physiological, viral, chemical, environmental factors; and the possible mitigation methods.
What Is It?
If you notice your tomato plant’s leaves curl, it may be a result of the Tomato Plant Leaf Curl Virus, indicating a viral infection. Typically, this virus gets transmitted via other infected plants or whiteflies. After getting infected, your plant may take up to 3 weeks before developing any symptoms.
However, there are several other reasons why your tomato leaves maybe curling. We will walk you through all of them in the next section. The most common symptoms include yellow leaves that curl upwards. Plus, the leaves may have a crumblier-than-usual texture. Long-term effects include stunted plant growth which may devolve the plan to take a bush-like look. The plant will not bloom any flowers or will drop away flowers. It will produce less and less fruits, which means fewer tomatoes for you to cherish.
What Causes Tomato Leaf Curl?
Tomato leaf curl or roll may be caused by a variety of reasons. Some of these invite more serious consequences than others. These include viral infections, physiological factors, chemical injuries, environmental stresses, or a variety of these factors. This implies that the symptoms differ with the particular reason why your tomato leaves are curling.
1. Physiological Leaf Roll
Physiological leaf curl happens when your plant experiences rampant top growth along with insufficient root growth. Leaf curl is then regarded as a common self-defense response among plants. This is because excessive cool or overly moist conditions cause leaves to roll upward and develop a leathery texture to resist this unnecessary cold or moisture. Herein, the leaves still uphold their natural green color.
This happens roughly around the fruit setting season and can be most frequently seen on pruned and staked plants. Leaves of your tomato plants may be curling because of the other side of extreme -uneven watering, dry spells, and soaring temperatures. In this case, leaves will curl upwards in order to conserve water but will not develop a leather-like appearance.
This is one of the most common reasons for tomato leaves to curl. This is a natural growth response when environmental conditions fail to provide the nutrition and water requirements of the plant. Some other factors which may cause physiological leaf roll are as follows – root injury, transplant shock, excess nitrogen consumption, over-pruning, and phosphate deficiency.
2. Chemical Injury Leaf Curl
Chemical injury may also cause leaf curl. This happens when herbicide residue remains inside the compost or mulch used in potting the plant. Some quantity of herbicides, fungicides, and hormone-based herbicides are required for optimal growth. Nonetheless, overexposure can damage your highly sensitive tomato plants. You need to take particular care in shielding your tomato crops for string winds can put your crop at risk of encountering chemicals stored in nearby farms.
Common symptoms of chemical injury are leaves rolling downwards that may get twisted, split stems, and chlorotic or yellowish deformed fruits.
3. Environmental Stresses
Sometimes leaf curl may be triggered by nothing more than environmental conditions such as speedy winds, low humidity level, and dusty air.
The leaf curl is a natural defense response that helps the plant avoid further water loss. You will witness a similar response if you fail to water your tomato plants. In cold and highly humid temperatures like during the rainy season, the tomato leaves will get thick, leathery, and curl inwards. This helps the leaves avoid excess water.
4. Leaf Curl Virus
If you witness abnormally stunted growth coupled with tomato yellow leaf curl, your plant may be infected with a virus. The leaf curling or twisting is generally erratic and follows no fixed pattern. Depending on the type of virus, your plant may witness other symptoms like yellow leaves, purple leaf veins, or browning of fruits from the inside.
Two of the most common viruses that affect tomato crops are the Tobacco Mosaic Virus (TMV) and the Tomato Yellow Leaf Curl Virus (TYLCV). These are infamous for spreading from humans, whiteflies, and aphids to the tomato crops.
How To Fix It?
There is no single reason why your tomato leaves are curling, which adds to the frustration of a tomato grower. The sure-shot way to fix leaf curl is correctly identifying its cause first. Before learning how to fix a leaf curl, let’s discuss ways to avoid your tomato leaves from curling in the first place.
To begin with, choose plant varieties that are naturally less prone to curling, or TYLCV resistant crops. Next, it is important to uphold adequate moisture in the soil. Take particular care in avoiding excess fertilizer, including nitrogen content, and prune indeterminate tomato varieties cautiously. It is best to avoid exposing your plant to high temperatures, by shading them wherever possible.
However, if your plant has already curled, not all hope is lost. You can still try and reclaim your tomato crop to its lost glory by reversing the leaf curl. It may take some time and effort, but you will be able to save the crop in most cases.
1. Regular Watering And Well-Drained Porous Soil
To help prevent and undo the physiological leaf curl, you must set a fixed watering schedule for your plants. We recommend you to water your tomato plants in the morning itself, allowing them to use the water to sustain themselves throughout the day.
Also, make sure that the soil is porous and well-drained to prevent mineral leaching which in turn leads to tomato leaf curling. If your plant has already suffered from physiological leaf curl, just fix its watering and soil requirements, and it will go back to usual within some days, given you act on time.
2. Avoid Herbicide Drift
As discussed above, herbicide overdose can cause chemical leaf curl. It is almost impossible to completely undo the damage caused by herbicides but you can always reduce its toxicity to best recover the plant.
As a preventive mechanism avoid spraying herbicides when wind speed is more than 5 mph. Also, makes use of a hooded sprayer. Once the damage is done you need to dilute its contribution to the soil. You can do so by regularly watering the soil and maintaining a well-drained surface. Doing so will at least prevent leaf curling in the new leaves that will grow.
3. Proper Shading
You can protect your plant from environmental stresses like high speed winds and scorching heat. Just place them under proper shade. This will help your plant recover and be safe from excessive dryness and dust. You will see a replenished plant within no time.
4. Additional Nitrogen Supply
If viral infestation is behind your tomato leaf curling, it may have caused leaves to fall. You can ensure a renewed, and healthy foliage by nourishing your tomato roots with some extra urea. The additional nitrogen will help it grow better.
5. Pest And Disease Control
Pests like broad mites and whiteflies are responsible for transmitting diseases between different plants like tomatoes, peppers, and potatoes. If you want to avoid disease infestation in your tomato crop, keep it free from the culprits, i.e., the pests.
You can use organic ways such as using natural predators like praying mantis and ladybugs and praying mantis. However, if the infestation is beyond damage control, go for insecticides. These will prove beneficial, despite risking killing some good insects and worms.
6. Crop Rotation And Intercropping
The most natural way to fix virus-related leaf curling is crop rotation. This will create an obstruction between two tomato crops, preventing the said viruses and bacteria from spreading and curling newer crops. This is because they will lose their activeness when you plant a non-susceptible crop like beans or carrots. This will break the vicious cycle and includes planting different crop varieties every season. Additionally, it will improve the soil structure and help maintain the nutrient balance.
Another effective mechanism is using the intercropping technique to combat pests and diseases, specifically soil-borne microorganisms. Marigolds are perfect partners for tomatoes due to their pest repelling qualities. You can also plant your tomatoes with Aphid repellant crops like onions and garlic. This will help prevent the spread of the said viruses since aphids are their known carriers.
Tomato plant leaves curl or roll up as a response to different stresses. These stresses may stem from physiological and environmental causes, viral infections, or chemical factors. It may be accompanied by several other symptoms depending upon its underlying cause. For instance, stunted growth and yellow, crispy leaves may signify viral infection.
However, it takes up to 3 weeks for the symptoms to visibly manifest. By the time you notice something is wrong, the condition may have been spread through the length and breadth of the plant. This makes it important for you to act at the sight of first symptoms if you want to save and fix the leaf curl.
You can prevent the leaves from curling altogether by planting the varieties resistant to curling, maintaining adequate soil moisture, nitrogen, and fertilizer content. Even if your tomato leaf has curled, you can still undo the damage by referring to the above-listed measures.
James Fields is the founder of Gardener to Farmer. His passion for gardening goes back to his childhood days when he would visit his grandfather during the holidays and help him with the plants in the backyard. This has now translated to creating a dependable resource for gardening.