Tomato leaf curls speak a lot about the tomato plant and its environment.
It is a primary indicator of physiological changes in the plant.
Here is some helpful information that elucidates the cause and intervention for the problem of leaf curling.
Why Are My Tomato Plant Leaves Curling Inward?
Inward curling of tomato plant leaves may occur on all the leaves of the plant or only at the points of new growth. The five primary reasons for tomato curls are wind damage, herbicide drift, herbicide residues, broad mites, or tomato viruses.
Causes of Tomato Plant Leaves Curling Inward
Wind damage occurs when high, dusty, and low humidity winds damage the leaves or stems of the tomato plant.
Leaves die back, twist, and curl in hot and low humidity environments.
Such environments may also lead to physiological leaf roll, which is the tomato plant’s self-defense gainst water loss.
With this physiological leaf roll, the tomato leaves, as well as its leaflets, slightly curl to protect themselves from more water loss.
Change of Seasons
When spring season turns to summer, the physiological leaves roll is seen first on the lower, older leaves, as an upward curling and inward rolling of leaves towards the midrib.
Reversal of the change happens when environmental conditions are corrected.
When the environmental factors persist, the whole plant is affected. The vine tomato cultivars are more prone to experience leaf roll.
There are several reported several causes that lead to physiologic leaf roll: phosphate deficiency, high nitrogen, heat, excessive water, drought, root injury, transplant shock, and pruning with dry soil conditions.
Proper hardening off tomato seedlings before planting, maintaining appropriate temperatures, use of right fertilizers while careful to avoid root damage and excessive pruning, planting different tomato varieties, and maintaining the soil’s moisture level are some measures that you can do to handle this problem.
Exposure to Chemicals
Tomato leaves curl as a symptom of chemical injury caused by exposure to chemicals such as pesticides, herbicides, or insecticides.
As a chemical factor, herbicide drift and herbicide residue affect the tomato leaves. Treatment of crops with herbicides is done to eliminate or prevent weeds.
Herbicide drift occurs when the herbicides sprayed for other plants are carried by the wind at speeds as low as five mph to other tomato gardens or plantations.
Herbicides such as glycophospahates and growth regulators, for example, 2,4-D and Dicamba, are sensitive to tomato plants even in low quantities.
As a result, the plant may look healthy after being in contact with the herbicide but have low and poor quality yields.
Herbicide residues can damage tomato plants in compost or mulch made from manure or hay in the fields sprayed with Grazon Next HL, Grazon, or GrazonNext.
Manure from animals consuming Grazon treated hay also contains Grazon residues and can affect the tomato plant when the manure is used. Therefore, these products come with instructions not to be used on vegetable plants and care to be taken when used on other crops.
Farmers are also advised to wait until 18 months are over for them to use manure from animals that consumed Grazon containing hay.
Symptoms of Herbicide injury
The herbicide injury symptoms are downward rolling or twisting of leaves, split, thickened, twisted, hardened stem, chlorotic plant, and deformed fruits.
The extent of damage depends on the quantity of the chemical exposure. The tomato plant can recover if only a little herbicide gets to it, although the yield still suffers.
The fruit from a chemically injured plant may not be safe for consumption. Therefore, it is vital to observe the label instructions to avoid chemical injury to the plants primarily.
How to Prevent Chemical Injury
- Other ways to prevent chemical injury include applying herbicides during low wind speeds (2mph) and observing the wind direction so that the chemical does not spread to other plants.
- In addition, the use of harmful herbicides near tomatoes should be avoided. You can also use a buffer zone to prevent herbicide drift. The buffer zone allows large droplets to settle before reaching the sensitive tomato plants.
- It’s also essential to avoid highly volatile herbicide formulations close to the sensitive tomato plants, and temperatures should be considered. The herbicides are applied at temperatures lower than the label temperatures to reduce vaporization and droplet evaporation.
- Wide-angle nozzles should be used and kept closer to the soil, and a boom shield used to reduce off-target sprays in the field. Application speeds should also be lower to minimize the incidents of herbicide drift.
- To prevent herbicide residue, always ensure that manure or mulch added to the garden has not been contaminated with chemicals that could damage the tomato plants.
- Agricultural workers should also wash their hands thoroughly after handling chemicals that can cause adverse effects to tomatoes before touching the tomatoes to prevent cross-contamination. Alternative safe herbicides can be used for weed control in areas close to tomato gardens.
Broad mite (Polyphagotrsonemus letus) damage is a biological factor. Broad mites attack several plants apart from tomatoes, such as eggplants, potatoes, cotton, citrus, and pepper.
They also affect ornamental plants such as zinnia, chrysanthemum, dahlia, Schefflera, and pittosporum.
These mites can be controlled using horticultural oil and insecticidal soap, alternating with predatory mites that attack and consume them.
Another biological factor is the tomato viruses, which can cause both leaf curling and stunting of tomato plants.
The viruses cause leaf curling, which at the initial stages is confused with phenoxy-based herbicide damage and yellow-green hue pattern on leaves.
The geminiviruses are the most common virus associated with the problem.
There is no treatment for tomato viruses, and mitigation measures include removing and destroying affected plants or controlling the weeds and disinfecting the garden tools depending on the virus.
Frequently Asked Questions About Why Are My Tomato Plant Leaves Curling Inward
What Causes Tomato Leaves to Curl?
Environmental, chemical, or biological factors may cause tomato leaf curling. Environmental factors lead to self-defensive mechanisms by the plant for survival through physiological leaf roll. This mechanism is how they adapt to environmental conditions that keep changing. Chemical factors include contamination of plants with pesticides, herbicides, or insecticides that are harmful to them. Biological factors include pests on the plants such as the broad mite or the tomato virus from whiteflies.
Why Are the Bottom Leaves of My Plant Curling?
Leaf curling occurs due to environmental stressors such as excessive moisture, heat, drought, transplant shock, severe pruning, and root damage. This change is the first sin in lower older leaves on the tomato plant.
How Do You Treat the Tomato Leaf Curl Virus?
Tomato leaf curl virus cannot be treated. The intervention involves preventive measures such as using a virus and white-fly free tomato transplants. When a tomato plant contains the virus, it is removed and destroyed.
Tomato leaves are sensitive indicators of environmental, chemical, and biological effects on tomato plants.
Symptoms of curling, folding, or rolling of the leaves are primary indicators that something is not right with the plant.
Early diagnosis and intervention on the problem can go a long way towards preventing adverse effects on the whole plant, depending on the cause of the problem.
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Daniel has been a plant enthusiast for over 20 years. He owns hundreds of houseplants and prepares for the chili growing seasons yearly with great anticipation. His favorite plants are plant species in the Araceae family, such as Monstera, Philodendron, and Anthurium. He also loves gardening and is growing hot peppers, tomatoes, and many more vegetables.