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Tomato Curling Leaves – Causes And Effects Of Tomato Plant Leaf Curl

Tomato Curling Leaves – Causes And Effects Of Tomato Plant Leaf Curl


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By: Nikki Tilley, Author of The Bulb-o-licious Garden

Are your tomato leaves curling? Tomato plant leaf curl can leave gardeners feeling frustrated and uncertain. However, learning to recognize the sign and causes of curling tomato leaves can make it easier to both prevent and treat the problem.

Tomato Plant Leaf Curl Virus

Curling tomato leaves may be a sign of a viral infection. Normally this virus is transmitted through whiteflies or through infected transplants.

Though it can take up to three weeks before any symptoms develop, the most common indicator of the disease is the yellowing and upward curling of the leaves, which may also appear crumple-like. Plant growth soon becomes stunted and may even take on a bush-like growth habit. Flowers usually will not develop and those that do simply drop off. In addition, fruit production will be significantly reduced.

Other Reasons for Tomato Curling Leaves

Another cause of tomato plant leaf curling, also known as leaf roll, is attributed to physiological conditions. While its exact cause may be unknown, it’s believed to be a sort of self-defense mechanism.

During excessively cool, moist conditions, leaves may roll upward and become leathery in an effort to repel this excessive moisture. This specific condition occurs around fruit setting time and is most commonly seen on staked and pruned plants.

Curling tomato leaves may also be triggered by just the opposite—uneven watering, high temperatures, and dry spells. Leaves will curl upward to conserve water but they do not take on the leathery-like appearance. Plum and paste varieties are most commonly affected.

Cure for Tomato Leaves Curling

Although physiologic effects for tomato leaf curl do not affect the overall growth or crop yields of plants, when the tomato leaf curling is due to a viral infection, removal of the infected plants is necessary.

You should also destroy these tomato plant leaf curl infected plants to prevent any further transmission to those nearby. The key to managing tomato leaf curl is through prevention. Plant only pest and disease-resistant varieties. Also, protect garden plants from possible whitefly infestations by adding floating row covers and keep the area free of weeds, which often attract these pests.

Looking for additional tips on growing perfect tomatoes? Download our FREE Tomato Growing Guide and learn how to grow delicious tomatoes.

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Why Are My Tomato Seedlings Leaves Curling?

While growing my tomato seedlings, I found some of the leaves were curling. I panicked a bit and wanted to find out what is causing it and how to fix this. This post contains my research on figuring out a solution to this problem.

Why are my tomato seedlings leaves curling? Your tomato seedlings leaves may be curling because they are facing too much heat, windy conditions, lack of water, overwatering, fewer nutrients, over-fertilization, viral disease, fungal disease, herbicide, or insect infestation.

If you find your tomato seedlings are curling, don’t panic. Find out what is the cause of this problem and you can figure out a solution that helps your tomato seedlings.


Common Causes for Tomato Leaves Curling and How to Manage Them

Tomato Viruses

Leaf curl (leaf rolling) in tomatoes may be a classic symptom of viral infection. The virus transmission can be through infected transplants or from insects like whiteflies.

The tomato yellow leaf curl virus, that causes the young leaves to appear cupped and pale green. This virus also causes stunted plant growth, purple leaf veins especially on the underside, yellow leaf edges and, low fruit production.

On the other hand, the tomato mosaic virus causes leaf curl/ rolling alongside other symptoms like mottled-colored leaves, small-sized leaflets as well as browning of the interior of the infected fruits.

Although there is no treatment for viral infections in tomatoes, there are several ways in which you can control the viruses. First and foremost, remove and destroy the infected plants.

Also practice regular weeding to minimize transmission through insects and, disinfect your garden tools more regularly to curb the mechanical transmission of the viruses.

Herbicide Drift and Herbicide Residue Damage

Tomatoes are sensitive to herbicides and off-target herbicide drift may happen especially with herbicides such as Dicamba or, 2,4-D or when you use contaminated compost containing pasture herbicides like aminopyralidp, clopyralid or, icloram.

In most cases, herbicide damage in tomatoes varies with the type of herbicide. New growth is usually affected first and starts to show symptoms like cupping leaflets and downward bent petioles.

Although you cannot reverse herbicide drift and damage, the tomato plants that survive the herbicide injuries can produce new normal growth.

Caution: Be very careful every time you spray an herbicide, as it may drift much further than you expect.

Excess moisture in the soil

Tomatoes just like many other crops prefer well-draining soils and if you fail to meet this condition, the soil might become saturated with water. Once this happens excessive moisture condition is created around the root system.

The excess moisture gets rid of the air pockets in the soil thus favoring infections such as root rot. In this case, your tomato leaves curl downward and change color from green to brown and in the end, they droop.

To avoid this, you need to practice good watering habits so that the soil isn’t too dry or too soggy for your tomatoes to thrive.

Pro Tip: Always check how soggy the soil is using your finger or a moisture meter and allow the soil to drain fully before your next watering.

Inadequate soil moisture/ under watering

Tomato plants prefer evenly moist soil and a slight dry-down before the next watering. When stressed by low moisture levels, the tomato leaves curl upwards in an attempt to reduce water loss through transpiration.

Persistent insufficient moisture causes the tomato leaves to wilt, turn yellow, then brown and finally they die.

Soil moisture is determined by the soil type and with loose soils such as sandy, drainage is rapid therefore, if you have such kind of soil, increase watering frequencies when the weather is hot to maintain adequate moisture in the soil.

Severe Pruning

It is good to prune your tomatoes during cool weather conditions by either pulling out those that are done with production or prune the old ones to produce flowers and fruits again.

Avoid pruning your tomatoes during summer as this exposes the interior of the tomato plants to strong sunlight and high temperatures which might cause leaf scorch and eventual death of your plants.

Prune your indeterminate tomato varieties conservatively/ lightly after they finish the fruit set. This makes them stay smaller and encourages new growth for more flowers and fruits.

On the other hand, determinate tomatoes do not require pruning as they stay smaller and produce fruits all at once and pruning affects neither the plant vigor nor the fruit size.

You just need to remove all suckers below the first flower cluster because when you remove those above, you'll destroying potential fruits.

Pro Tip: Always use sterilized pruning shears to prune your tomatoes. Also, remove only about a third of the plant and leave enough leaves to reduce exposure to too much sunlight.

Transplant Shock

Even though tomatoes are relatively tolerant of transplanting, they easily get shocked by the loss of roots due to rough handling, or major changes in environmental conditions when transplanting.

That’s why we recommend that you handle your tomato plants with care and harden off the seedlings before planting them in the garden.

To harden off your tomato seedlings, put them out in the area where they will be planted for progressively longer periods each day for several days (1 to 2 weeks before transplanting). This allows your plants to gradually adapt to the new growing conditions such they do not suffer transplant shock.

You must also avoid root disturbance as much as possible for both transplants and established plants. Also pay attention to environmental changes such as changes in temperature, sunlight, or moisture levels and take the necessary precautions to protect your tomato plants.

Insect Damage

Insects such as aphids and broad mites might also be the reason why your tomato leaves are curling. Aphids, for example, sack sap from the underside of the tomato leaves and stems using their mouthparts. The leaves then start curling and if left unmanaged aphid damage may lead to stunted growth and low yields.

On the other hand, broad mites attack young tender leaves making them turn brown and curl up. Just like aphids, you can easily identify broad mites on the leaves through damages and webs on the underside of the leaves.

To control mites in your tomatoes, spray the plants thoroughly with insecticidal soap or horticultural oil. Make sure that the spray reaches the underside of the leaves and the buds.

Also, here are the best companion plants for tomatoes some of which will help you get rid of aphids and mites.

Over-fertilization

Tomato leaf curling could also be an indication of too much fertilizer. As far as over-fertilizing goes, the lower leaves of your tomatoes roll upward until the side edges touch. The affected leaves then become thick and leathery.

Although leaf curl due to over-fertilization has no serious effects on flavor and fruit color, it might lead to tall and spindly plants with deep green foliage and few flowers, especially with excess nitrogen.

To control excess nitrogen in the soil, carry out repeated deep watering to leach out the fertilizer from the tomato root zone.

Tomato Variety

Given similar conditions, indeterminate tomatoes (vine varieties) are more likely to exhibit physiological leaf curl than determinate varieties (bush varieties). Therefore, select tomato varieties that are less prone to leaf curl.


Wind Damage

In addition to hot weather, windy and dry weather can cause tomato leaves to curl in a similar fashion. Excessively windy conditions can stress both the leaves and stems of your tomato plants.

If you are planting in an open field, this could likely be your issue. Strong winds can steal moisture from the plants, usually causing the leaves to twist and curl.

The solution is to provide some protection from the wind. This can be done by planting sturdier plants like bushes or trees to take the brunt of the breeze. Use a weathervane or similar to learn the typical direction of wind in your location and plant accordingly.


How to Control Tomato Leaf Virus

  • Look for disease-resistant varieties to prevent problems with tomato plants.
  • Plant tomato cultivars less susceptible to leaf roll
  • Mulch to maintain consistent soil moisture
  • Avoid heavy pruning fo tomatoes
  • Water as necessary

Given that this virus is spread by silverleaf whiteflies, controlling the spread of the virus has to do mainly with controlling the spread of these insects.
Try and prevent whiteflies from attacking your plants by creating a trap for them.
A 12”x12” board painted in yellow will attract the whiteflies.
Spread petroleum jelly on this board, to catch the whiteflies before they attack your plants.
However, this may not be an effective preventive measure and will not work once plants become infected.
An alternative organic option is to spray an insecticidal soap every two to three weeks.
If a plant has been affected by the tomato leaf curl virus, take steps to ensure it can be spread to other plants.
This requires covering the infected plant in a bag to trap any potential whiteflies inside and burn the plant to keep others from feeding on it and catching the infection.


Curled Leaves Due to Diseases

There are a number of diseases that can affect tomato plants, and some of them will cause curled or twisted leaves, including:

  • Bacterial Wilt of Tomato
  • Tomato Blight (Early & Late)
  • Tomato Yellow Leaf Curl Virus
  • Tomato Curly Top Virus

Bacterial Wilt Of Tomato

According to Wikipedia, Bacterial Wilt is a number of diseases that affect many plants, including:

  • tomato
  • pepper
  • potato
  • eggplant
  • cucumber

In tomatoes, Bacterial Wilt is caused by Ralstonia Solanacearum. This bacterium infects plants by damaged roots or by carriers (such as root-knot nematodes).

Bacterial Wilt of Tomato is caused by Ralstonia Solanacearum.

The disease is most common in moist soil at temperatures over 85 degrees Fahrenheit (30 degrees Celsius).

The first signs are a few leaves on top of the plant wilting and curling. Later, the entire plant wilts.

Finally, the stem turns brown. The plant’s growth may also be stunted throughout this period.

Bacterial Wilt clogs the vascular system of a tomato plant. This prevents it from moving water and nutrients through its tissue.

Eventually, the plant will succumb to this disease. There is no cure, so it is best to remove infected plants right away to prevent the disease from spreading.

Choose resistant tomato varieties (such as Neptune or Tropic Boy) to avoid the disease.

Tomato Blight (Early & Late)

There are two types of tomato blight:

  • Early Blight – caused by Alternaria tomatophila or Alternaria solani. Early blight spreads more rapidly in damp conditions, such as after rainy weather, watering your garden, or heavy morning dew.
  • Late Blight – caused by the fungus Phytophthora infestans. It spores spread on the wind, and it does well in cool, wet conditions, with an ideal temperature range of 60 to 70 degrees Fahrenheit (16 to 21 degrees Celsius).

Early blight causes brown spots on leaves.

Of the two diseases, late blight is easily the more fatal for tomato plants.

Late blight is much more deadly to tomato plants than early blight.

Tomato Yellow Leaf Curl Virus

According to Wikipedia, tomato yellow leaf curl virus is found in tropical and subtropical regions. It causes leaves to twist and curl, and is transmitted between plants by the whitefly.

One way to prevent the spread of this virus is through the use of insecticides. If you find that you have infected plants in your garden, you will need to pull them out and destroy them.

The whitefly can transmit tomato yellow leaf curl virus between plants.

Do not compost the infected plants, since the virus may survive in your compost pile and infect your garden in subsequent years.

Tomato Curly Top Virus

This virus is transmitted by the sugar beet leafhopper, and it affects beets, tomatoes, spinach, peppers, beans, potatoes, and cucumbers.


Summary

They key to solving the problem of twisted or curled leaves is to identify the source or sources of the problem. Wind damage will resolve once conditions improve. Mites and viruses can be identified by laboratory analysis. Damage caused by herbicide drift or residue in mulch and compost is the most difficult to identify. Regardless of the cause, curled or twisted leaves on tomatoes or other vegetables are a sign that you may need to take action to save your crop.

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