Are your tomato leaves curling and you have no idea what could be the cause?
Tomato leaf curl can be due to several reasons including; insect damage, inadequate soil moisture, excessive fertilizer application, viral infections, improper pruning, herbicide damage, and drift, as well as transplant shock.
Some of these causes are more serious than others and they can leave you uncertain about what is the problem.
However, the article you are about to read touches on the common causes of tomato leaf curl/ roll and how to manage them. In it, you will find easy ways to identify, prevent and treat leaf curl in tomatoes.
Sounds interesting right?
Let’s get to it.
Common Causes for Tomato Leaves Curling and How to Manage Them
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.
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.
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.
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.
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.
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.
You have just read an article on tomato leaves curling and has seen why this happens and how to control it.
In summary, avoid tomato leaf curling by;
- Selecting tomato varieties that are less prone to leaf curl
- Pruning indeterminate tomato varieties conservatively
- Maintaining adequate soil moisture
- Avoiding high temperatures by shading your tomato plants
- Protecting your tomatoes from insects and pests
- Avoiding over-fertilizing your tomatoes, especially with nitrogen
Back to you.
Do you have any more thoughts why tomato leaves curl/roll? Let us know in the comments below.