Why do tomato leaves curl? (How to prevent it for good)

Gardeners frequently become concerned when they notice changes in their plants. Specifically, TOMATOES are susceptible to various viruses and environmental factors. Have you seen the leaves of your tomato plants starting to curl? Such a phenomenon could be the result of biological, chemical, or environmental causes.

Extremes of temperatures cause tomato leaf curls. Too hot, too cold, or very dry or very wet. To combat Tomato leaf curl, grow indoors, ensuring constant temperatures and adequate moisture is available to the plants during the initial stages of growth.

Table of Contents

Tomato leaf curl can affect the newly developing or all the plant leaves. The curling usually starts with a few leaves and then progresses to the entire plant. Tomato leaf curls can also take different forms: upwards or downwards. There are many known causes for tomato leaf curl, and they include:

  • Damage from wind
  • Herbicide drift
  • Herbicide residue
  • Broad mite
  • Tomato viruses
two red tomatoes on the plant

This article will focus on these causes independently and their preventive measures.

Tomato leaf curl can be caused by damage from winds

Tomato leaves curl up due to high winds, which blow dust, causing low humidity and water loss through the leaf surface. The condition is usually called physiological leaf roll. Other factors, such as heat and low moisture, also cause it. With this condition, the leaves curl up in self-defense to protect their surfaces from further moisture loss.

The intensity of leaf rolling determines the impacts of the same on yield and quality. In severe cases, the plant flowers may drop, lowering fruit formation. If the rolling is not extensive, the plant usually improves once the environmental conditions normalize.

When the leaves of the plant curl, they are less effective in manufacturing food for the plant. This is because the surface, which usually traps light for photosynthesis, is no longer exposed. As a result, plant growth gets slower. Wind can also cause low temperatures, which are not conducive to the plant’s development.

Moderate wind is necessary for the healthy growth of your plants. Some benefits of wind to your plants include sufficient air circulation, preventing moisture from developing on the foliage surface, causing fungal diseases on your plants, and pollination.

Wind also carries tomato blight spores, and this is just as problematic. This blog post I wrote covers that disease in detail.

Severe winds can, however, kill young tomato plants. For this reason, you need to protect your plants from wind damage. We will now examine how the wind will likely damage your tomato plants.

Gardening designs to prevent tomato leaf curl

The location of your garden is critical in preventing your plants from wind damage. As you choose where to set up your garden, you need to look into the intensity of the wind in that area. If the wind is a serious problem, you can set up your garden near a shield such as a wall, fence, or trees. If you can’t find a shield, you must create one.

Additionally, you can set up your garden so the wind flow is regulated. If you are growing your plants in a container, it gets easier as all you need to do is relocate them to a less windy location. Growing your plants in a moving tray will make it easier to move them around.

Make use of windbreak during the garden design phase.

This form of protection is usually temporary. It could be made of cloth, wire mesh fabric, or woven wood panels. As you use windbreak, ensure it doesn’t affect the plant’s access to sunlight. Also, certain windbreaks can cause the space within the garden to heat up, causing other problems such as diseases and high humidity levels, which affect the development of the plants.

Tomato leaf curl is a troublesome disease for tomatoes. Still, it is not the only one, and if you are suffering from any other diseases, check out the video below, where I take you through everything you need to know about tomato diseases.

Herbicide drift which affects tomatoes

Low wind levels of 5 mph can carry herbicides for a mile, causing herbicide drift and severely damaging tomato plants. This occurs when herbicides used in treating other plants, such as cotton and corn, land on the surface of your tomato plants.

Even broad-spectrum herbicide weedkillers for lawns, such as glyphosate and growth regulators, can affect tomato plants causing these symptoms.

Tomato plants are sensitive to these herbicides, and concentrations as slow as low as 0.1 ppm can affect your plants. The yield is usually affected even if your plants physically recover from herbicide drift.

The leaves of TOMATOES already injured by herbicides such as 2,4-D can never be treated and will usually never recover. If the growing leaves are also affected, you must harvest the fruit and eliminate the plant. However, recovery is possible for young plants within six weeks of harvesting.

Nonetheless, if new buds don’t start showing improvement within a week, you should consider uprooting the affected plants and replanting.

How to protect your tomato plants from herbicide drift

Damages from herbicide drift are often irreversible, especially for older tomato plants. For this reason, the farmer or gardener should work on the following preventive measures to protect the plants from possible exposure:

  • Take note and follow herbicide manufacturers’ instructions, including the dosage.
  • Avoid using herbicides when windy, especially when the wind blows toward tomato plants.
  • Always use a hooded spray when using postemergence herbicides growing near tomato plants.
  • Always spray at low pressure to increase the size of droplets and reduce their ability to go with the wind.
  • You can also spray at lower speeds to reduce the movement of the spray in the air.
  • Wherever possible, include spray additives.
  • Use the most appropriate spray nozzles for the chemical, and always wash out all the substances from previous applications before and after using the spray tank.

Herbicide residue can potentially cause tomato leaf curl

Tomato plants are sensitive herbicides left in mulch and compost made from previously sprayed Grazon, GrazonNext, or GrazonNext HL. The chemical compound in these products is aminopyralid, which can remain active for nearly two years.

The same compound can also be transferred in manure from animals that feed on treated plants. Unfortunately, this compound is commonly applied in waste as it is used in pastures to kill broadleaf weeds.

Suppose you read the instructions on this product. In that case, you will realize that the plants collected from the sprayed fields are unsuitable for vegetable manure.

Additionally, gardeners who sell hay or manure should notify buyers that they used the aminopyralid chemical. As a buyer, you also need to find your hay or manure source and the type of chemical.

Preventive measures for your TOMATOES against herbicide residue

  • Avoid using aminopyralid-treated plant residues, haw or straws within the 18-month window.
  • In mushroom spawn, compost or mulch, avoid using manure from animals fed on treated forage or hay within the previous three days.
  • Avoid planting tomato plants in fields treated with aminopyralid and manure that could contain the chemical product.
  • Aminopyralid breaks down faster with warm moist soil; watering compost and burning plant residues could speed up the herbicide decomposition.

A world without tomatoes is like a string quartet without violins.

Laurie Colwin

Damage from broad mites

Broad mites affect tomato plants, among other vegetables. They are 0.10 to 0.30 millimeters long, oval-bodied, and yellow to translucent. These organisms feed on the young leaves of TOMATOES and flowers without light. Since they are light-sensitive, broad mites commonly affect plants grown under shade or in greenhouses.

As the pests feed, they inject the leaves and flowers with chemicals that distort and twist the plant leaves. It is difficult to diagnose this problem because the pests are invisible to the eye and are often missed under a magnifying glass. Moreover, the damage appears like any other on the tomato plant.

However, severely affected plants will have the leaf or fruit underside bronzed or rusted. For this reason, they are often discovered when the damage is extensive. You can look for the eggs on the tomato leaves for early diagnosis; they are usually white, oval, and bumpy.

Broad mites develop and multiply fast, with eggs developing into adults within six days in hot weather and up to ten days in the cold. However, they are affected by weather conditions such as sunlight, so they will rapidly come and go.

Broad mites affect tomato plants from the legs and antennae of whiteflies whenever they land on them. You can also transplant infected plants from greenhouses. There is no possible recovery for severely damaged tomato plants. For this reason, the farmer needs to uproot and dispose of it.

Treatment for broad mites

  • If the plants are moderately damaged, you can treat them with sulfur-based miticides- if the tomato cultivator is tolerant.
  • Additionally, you should avoid treating tomato plants when water-stressed or at a high temperature above 90F, as they can suffer further damage.
  • You can also use other compounds to treat broad mites, such as Horticultural Oils and Insecticidal Soaps.
  • Predatory mites are the most effective, providing a lasting solution to broad mite attacks.

Tomato viruses

A wide range of tomato viruses can cause tomato leaf curls. Tomato leaves affected by viruses can be initially confused with phenoxy-based herbicide damage. However, yellow-green mosaic patterns form on the leaves as the disease progresses.

The most common tomato viruses causing tomato leaf curl include those in the geminivirus group, such as the tomato yellow leaf curl virus commonly found in Texas. Whiteflies normally transmit this form of the virus. Other tomato viruses that cause tomato leaf curl include:

  • Tomato yellow streak virus
  • Tomato yellow mosaic virus
  • Texas pepper virus
  • Sinaloa tomato leaf curl virus
  • Potato yellow mosaic virus
  • Pepper huasteco virus
  • Tomato leaf crumple virus
  • Chino del tomato virus
  • The tomato yellow leaf curl virus

Another major virus that tomatoes suffer from is Septoria Leaf Spot. This will kill the plants. In this article, I will show you how to identify it and all the remedies to treat it effectively.

If you are concerned about a virus infection in your tomato garden, look for new tomato varieties that are more resistant to viruses. Unfortunately, you will not find an utterly immune cultivator.

The other option is using insecticidal oils and soaps to control whiteflies that cause tomato viruses.

tomato disease

Prevention of tomato viruses

Other possible causes include the following:

  • Transplant shock; this occurrence is expected due to root damage, and it occurs once you transplant your seedlings from the nursery.
  • Excessive pruning; pruning is helpful in some cases, but it can potentially cause stress to the plant due to more exposure to heat. Excessively pruned tomato plants can recover on their own.
  • Excessive nitrogen; too much nitrogen fertilizer applied during the fruiting stage can cause the leaves to start curling. At this stage, you should only use phosphorous and potassium fertilizers.

Conclusion

Tomato leaf curl is a sign that something is not okay, and you need to step in in time to save the plant. You need to identify the cause of the problem to manage it. Some issues, such as physiological damages caused by wind, will go away independently depending on the severity.

Herbicide-related damages must be avoided as they can severely damage the crop. As for broad mites and viruses, you must control the causing agent, often whitefly. If unsure of the cause, you should seek professional help and lab analysis.

Tomatoes are great to grow, especially if you follow the basic rules and methods. I wrote a detailed article on growing tomatoes at home to ensure perfect results every time. Read that here.

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