Leaf curling in tomato plants can be a worrying symptom for any gardener. This symptom can translate into a big concern for anyone doing tomato production in fields. Learn more about leaf curl patterns (up, down or rolling) in tomatoes, their causes, and how to control, stop or prevent the problem where possible.
1) Herbicide Injury Or Residues
Certain herbicides are applied in a tomato plantation to control weeds. The plant responds in various ways if there is direct leaf contact with the spray. For instance, the leaves may yellow, discolor or bleach; twist, curl or roll down and wither. Petioles can exhibit drooping while stems could bend. The stem may also develop a twisted growth, crack or develop bumps with lesions.
This may occur because the plant absorbs harmful chemical compounds via stomata or roots. The plant’s physiological processes are also interfered with. Herbicide residues in the soil can also lead to similar problems in the long run.
The duration within which expected specific symptoms may vary. Typically, it can take anything from three days to two weeks.
Common herbicides known to cause this injury include 2, 4-D, picloram, dicamba, Aminopyralid, clopyralid and phenoxyacetic acid. Have a look at the pictures below to identify the curling patterns.
How to Stop Herbicide Injury/Damage
The best way to solve herbicide injury is by preventing it. Here is how you can avoid tomato plant damage due to herbicide application.
- Avoid spraying in your garden during windy weather
- Do selective herbicide application if you are controlling narrow-leaf weeds
If you want to rule out any other cause apart from herbicide injury, here is a how-to list to help you track it down:
- Record the date when you sprayed the herbicide
- Examine the newly formed leaf margins or petioles and stems of tomato plants that exhibit symptoms
- Pay attention to any patterns of symptoms but don’t limit to them curling
- Look for similar symptoms in a different plantation where the specific herbicides have been used e.g. tobacco field
- Always counter-check when (date) you applied any nitrogen fertilizers with the dates when you applied herbicides
Can herbicide injury be reversed? If plants are not killed, new side shoots would emerge. However, if the damage is severe, the injury cannot be reversed. The plants dry up and die.
2) Tomato Mosaic Virus (ToMV)
Another cause of tomato leaves curling is the tomato mosaic virus. Because there are various strains of viruses that cause ToMV, symptoms might differ. Even though, mosaic viruses that attack tomatoes produce many similar symptoms at any stage of growth.
Below is a breakdown of symptoms in tomatoes caused by the virus strain aucuba.
Leaf veins, petioles, and parts of the leaves turn light green or appear light-colored. Leaflets may wrinkle. Leaves often display curling-down patterns. They have deformed shapes and reduced leaf sizes.
Flowers may drop off.
Uneven fruit ripening characteristic of green spots of varying hues. These spots may be produced internally or externally,
Conditions during the tomato growing season must be surveyed to help differentiate symptoms.
How to Fix Mosaic Virus in Tomatoes – Prevention
It is quite difficult to treat mosaic viral diseases. Therefore, prevention is the best cure option.
The use of more resistant tomato varieties is the most effective preventive practice known. Here are more how-to good prevention practices:
- Remove the infected tomato plants together with their debris and destroy them. Do this after every growing and harvesting season.
- Avoid handling the infected plants, plant parts, or seeds together with other healthy and disease-free seedlings, gardening or cultivation tools
- Wash-clean and disinfect and gardening tools after each use in a suspected area. Do the same for your staking systems (trellises, cages, wires, etc.).
- Get rid of aphids and thrips after transplanting your tomatoes. These insects can transmit mosaic viruses from infected plants or tobacco fields.
- Inspect tomato seeds and all mosaic virus-vulnerable planting materials before you buy.
- Continue scouting your healthy tomato garden often to enable you to take notice of infection symptoms
3) Verticillium Wilt in Tomatoes
Verticillium wilt is a soil-borne fungal disease caused by Verticillium dahlia. During the early stages of verticillium wilt, older lower tomato leaves turn yellow. Other symptoms of infection include:
- Stunted tomato plants
- Leaves curling up starting from the margins
- Foliage loss
- Presence of brown to black streaks on the water-conducting vessels
- Sometimes the water vessels may discolor
How to Stop Verticillium Wilt – Best Control Methods
Managing verticillium wilt is the most effective substitute for treatment since the disease has no known cure. Here is how you can manage it:
- Select resistant tomato plant varieties
- Crop rotation involving planting less vulnerable grasses
- Remove and burn all infected tomato plants
- Practice clean weeding to get rid of hiding host plants
- Subjecting topsoil to high-temperature heat, especially in dry areas
4) Septoria Leaf Spot of Tomato
Septoria leaf spot is a fungal plant disease. It is caused by the fungus Septoria lycopersici. The disease reproduces through spores.
Septoria leaf spot spores are spread mainly by splashes of rainwater, insects, and equipment and through workers’ hands. The spores germinate upon landing on your tomatoes at room temperature. Infection occurs via leaf stomata.
Symptoms in Tomatoes
Small grey spots usually mark the first symptom of infection. These spots form on the old lower leaves inside the first week of infection. They become larger. As the infection develops, more damage is done to the leaves. As a result, leaf areas surrounding the enlarged spots start to yellow. With severe infection, curling patterns begin from leaf edges, curling up.
Many small brown pimple-like swellings form at the center of spots. Later on, tomato leaves turn brown and wither. Leaves dry up and drop off eventually.
How to Fix With Treatment
You can treat this fungal disease with the use of registered fungicides. They are sold by different names such as Chlorothalonil, Maneb, Mancozeb, or Benomy.
How to Stop: Managing Septoria Leaf Spot
Managing septoria leaf spot is mainly done through cultural practices. They include:
a) Use Clean, Disease-Free Tomato Seeds: Purchase sowing seeds from disease-free zones located within your area. Use clean hands as well as and cultivation tools to avoid contamination.
b) Clear Weeds and Plant Debris: Before you start a new seedbed or nursery, clear all possible host plants such as jimsonweed. Clear all tomato plant remains from the previous growing season. Collect these together and destroy them in fire or spay fungicide.
c) Practice Tomatoes and Host Crops Rotation: If you have a potato plantation, allow a 3 – 4 year gap before you can plant tomatoes.
d) Break Fungal Cycle & Disease Development: First, remove lower suckers and older leaves. Second, properly space tomatoes according to the variety you have planted. Spacing can help stop the disease from developing further.
5) Physiological Tomato Leaf Curl (Rolling)
Physiological leaf roll or curling is not caused by a disease. Instead, it is a way in which plants respond to the changes in conditions around them. These changes are often called stress factors.
These physiological factors and stresses are as follows:
a) Leaf curl due to physiological or environmental reasons. One of the most common is dry blowing wind. Blowing winds means the rate of water loss by the plant will increase. Excessive water loss will lead to curling leaves.
b) Prolonged root exposure to wet soil or dry soils. Waterlogged soils cause root rot. Root rot impacts water absorption and trasportation. On the other hand dry soil, means your plants have little or no water to use. Often, this root stress is exhibited in older tomato leaves. They curl up with a leathery texture or feel.
d) Heavy or severe pruning when your tomato plants are growing fast or when they are heavily producing fruits.
Fast growth and heavy production means there is an increased demand for nutrients and water. If you have pruned severely, your tomatoes have less foliage. Therefore, it means that less food is available than what the plants actually require. As a result leaves will start curling. If rolling
e) Excess nitrogen in soil or nitrogen toxicity. Excess nitrogen fertilizers will lead to tomato roots stunting growth. This means the root growth is heavily affected. As a result, water and essential mineral absorption is greatly affected. Plants may respond by leaf tips burning and browning. Some tomato leaves may start yellowing.
f) The shift from one season to another while cultivating tomatoes. For instance, spring-summer transition can lead to tomato leaflets to start curling.
“Symptoms of leaf roll appear on lower leaves first, when the leaves roll upward and sometimes overlap.” UMass Extension Greenhouse Crops and Floriculture Program.
Tomatoes usually recover from leaf curl/rolling due to physiological stress. However, for this to happen, the stress factors should reduce first naturally, or appropriate action is taken to counter each of the above physiological stresses.
6) Tomato Yellow Leaf Curl Virus (TYLCV) Disease
The yellow leaf curl virus of the tomato is caused by begomoviruses. It is a popular tomato disease transmitted by the whitefly species (Bemisia tabaci). The virus can also be transmitted via infected seeds.
The viruses produce leaf curling and yellowing at severe infection stages. Leaf curling pattern is Some leaves may curl down. Besides tomatoes, other TYLCV plant hosts include peppers and standard beans.
Unfortunately, this infection cannot be treated as it has no known products.
Solving TYLCV in Tomatoes (Disease Management)
A single treatment alternative or approach cannot be effective and efficient. Treatments are expensive too. So, this calls for a combined effort to reduce the population of whiteflies and their migration. As a result, managing the disease this way becomes cost-effective.
You can manage the spread of TYLCV using the following simple framework.
a) Transplant seedlings and sow seeds free from TYLCV virus and whiteflies. This may be enhanced through purchase planting materials from a reputable supplier near you.
b) Apply insecticides or insect repellents for whiteflies. Consequently, this will reduce the whitefly population. As a result, foliage feeding is minimized and thus virus transmission rates are reduced.
c) Remove all infected tomato transplants with signs of TYLCV infection from the greenhouses and fields.
Enclose them in plastic bags to prevent transmission of the virus. This practice should be thorough. We recommend that you do this immediately before you start preparing for the new planting season.
d) Separate newly purchased TYLCV-free tomato cultivar/plantings from any garden plants known to be whitefly hosts.
Additionally, avoid planting both at the start of new tomato growing season.
e) Plant tomato varieties resistant to tomato yellow leaf curl virus. We advise going for these resistant varieties that are produced and well-adapted to conditions in your area.
For you to identify and confirm the virus, you should submit the affected tomatoes to a diagnostic laboratory for analysis.
References and Sources