The Reasons for leaf curl on apple trees

The Reasons for leaf curl on apple trees
The Reasons for leaf curl on apple trees

When the apple tree on your plot is well developed and pleases you with its beautiful foliage, your soul relaxes without you knowing it. You understand that you have made the right choice, that you have chosen a sapling and a variety that is properly fed and watered, and that the soil, by all appearances, apples like.

When our tree suddenly starts curling its leaves, it’s a completely different story. Obviously, so she’s not doing it from the outside, and there’s some reason for that. Therefore, let’s consider the most common causes of the sudden leaf curling of apple trees on the site and learn how to carry out preventive measures so that this phenomenon is no longer observed.

Also, familiarize yourself with the use of the safest and gentlest measures to eliminate the problem of leaf curl on apple trees and the measures involved.


There are many reasons why the leaves of young and several-year-old apple trees suddenly start to curl. These can be the mischief of aphids, as we are all more familiar with the common, or more rarely – red head disease, and Powdery mildew (a harmful fungal disease that happens to appear in cool, wet years) or Apple scab. Finally, the leaves on apple trees curl, and careless owners introduce not enough nutrients into the soil, and the apple tree mediocrely starved. Or he watered too little at the roots, hoping that once he moistened the soil surface, it would be quite enough. See how many reasons there are?

So let’s try to deal with the problem of leaf curl on apple trees one by one, starting with Red Aphids.

Red Aphids

Appletree varieties such as ‘Cripps Pink’, ‘Empire’, ‘Fuji’ and ‘Gala’ are the most actively attacked by Red Aphids. It is uncertain, and perhaps our readers will write in the comments why Red Aphids prefer the leaflets of these cultivars, but more likely it is a biological characteristic of the thickness of the leaflets of these cultivars.

In the case of Red Aphids and the time of their discovery, it is not always appropriate to use chemicals (insecticides). For example, when there is a large number of insects, i.e. beneficial insects, in the garden and we kill them with chemicals.

With this in mind, glue tapes can be installed on a large scale in gardens or small plots of land – especially at the end of April, at a height of 40-60inch (1-1.5m). These glue tapes eliminate aphids and the large number of ants, which are its carriers and which, when irritated by their tendrils, produce a sticky and sweet liquid, aphids, which ants feed on.

Often, instead of using more expensive trapping tape, imaginative gardeners use ordinary fly tape, preferably coated on both sides with a sticky substance female aphid dispersal tape is stuck (usually by accident), which helps to drastically reduce the number of pests.

In addition, you can kill a dozen “hares” with sticky tape: partially get rid of earwigs, English moths, leafroller caterpillars (which also curl up on apple leaves and pupate in them), and even apple blossoms, which get caught in sticky tape by accident because they are slow to respond.

To avoid or minimize the presence of aphids on your plots, you must keep a close eye on your apple trees and remove bark that is starting to peel off, as Red Aphids will scatter eggs in these areas and the voracious larvae will quickly hatch.

You may not think that simply hanging your belt once or hanging out the sticky ribbon like a wreath will be a relief. This is not the case. Both the trapping tape and the sticky tape must be replaced with new ones every five or six days or they won’t be of much use. For example, hang up the catch tape or sticky tape when you leave the countryside, and replace it with a new one when you arrive. But that’s not so bad: considering that the larvae don’t always hatch, but only three times a season, it means you only need to change the trapping tape three times, too.

There are also rules for setting up trapping straps to prevent Red Aphids. trapping straps must be as close to the trunk as possible because aphids are very small insects that can easily get in through the gap between the trapping straps and the wood. In order to get the straps to lay flat, you should first clean all the bark off the old and dead wood and then securely fasten the straps to the tree.

A couple of words should also be said about ants, we have been exposed to them earlier and told you about the preference of ants for the sweet-smelling secretions of aphids. So, in order to reduce the aphid population in an area, you need to reduce the population of these creatures in that area as well.

Unfortunately, you can’t do this without using chemicals because ants are poisoned using insecticides such as “broad-spectrum killers” or “acaricidal properties”. Of course, you can always take our grandparents’ advice and use soap or even cow urine to treat anthills, but as a rule, if it helps, it won’t last long.

Leaf curl on apple trees one by one, starting with Red Aphids
Leaf curl on apple trees one by one, starting with Red Aphids

The common aphid

If Red Aphids inhabited berry orchards more than scorned our apple trees, you could notice it by the red swellings on the leaves. Common Aphids, gathered in huge colonies, often spread by the same ants, simply attack the young growth.

It looks as if the young shoots are violently rubbed together with the leaves. So this happens because aphids suck the sap from young shoots and leaves, they become deformed, leaves stop growing, shoots bend, and photosynthesis is disturbed.

There are many ways to control aphids. They include the most diverse insecticides, treatments that can be carried out a month before harvesting the fruit by strictly following the instructions, as well as simple removal by cutting off the damaged part of the plant, as well as fighting ants, as we have already mentioned above, and of course following the planting plan of the plant. Avoid very dense planting and always remove weeds and even prune them, as they often cause aphids to attack the shoots.

Important note: Aphids are no joke: let them twist a few leaves and shoots – no harm, no foul – but they can actually spread all kinds of diseases to plants, even viral ones, and strong, healthy plants can perish from aphid trunk stings. So decide whether you want to deal with aphids with a little soap and pepper or get rid of them forever with a reliable insecticide.

Powdery mildew

Powdery mildew causes leaf curl not only on vegetable crops but also on apple trees. To detect the presence of Powdery mildew on an apple tree, you need to examine its leaves as carefully as possible, especially the young leaves, where Powdery mildew often settles: it may penetrate the young leaf tissue more easily, and it is more vigorous.

Powdery mildew usually manifests itself on apple trees in early spring. it is during this period that the plant should be examined more closely, and if you find white patches on the leaves reminiscent of Powdery mildew, you need to sound the alarm immediately and set about eliminating the disease, the end result of which is dry, curled and deciduous leaves.

Powdery mildew is particularly active during the warm and humid seasons, and of course, Powdery mildew spreads more actively in densely planted areas where apple and berry trees are located too close together, shaded from each other, aggressively watered, not pruned, and where the soil under the trees is not loosened. Apple Powdery mildew, which is not a terrible disease from the outside, can cause very serious yield losses, taking the yield of marketable fruit from 30% to 50%, which is already quite serious.

In no case should treatment be delayed after Powdery mildew has been detected on apple trees. If the leaves are strongly infected and there are many small leaves affected, it is better to use only approved fungicides (preparations against fungal infections), strictly following the instructions on the package, at least one month before harvest. As an example, one can cite the preparation “endophytic plant protection fungicide”.

Among folk remedies, which have proven to be more effective in suppressing its further spread than in eradicating Powdery mildew, you can recommend treating plants exclusively with a copper-based boom hand sprayer preparation, such as Bordeaux mixture at 1%. apple trees can be treated with this drug 20 days before harvest and immediately after harvesting all the fruit on the tree. However, do not place high hopes on the Bordeaux mixture; this preparation is supportive but not primary.

In addition, to minimize the occurrence of this infection next year, it is necessary to remove absolutely all plant remains, including fruit and small leaves, from the trees in the fall and, after repeating all these procedures in the spring, to burn them by all means behind the plot.

Apple scab

This is a fungal infection that most often affects apple trees and, to a lesser extent, pear trees, and can also cause leaf curl. The disease is spread by spores, so if the weather is wet and windy, Apple scab will quickly infect most apple plants on your property.

The first sign of Apple scab on the leaves of apple trees is the appearance of an olive-colored scum on the leaves. In addition to the gradual distortion of the leaves, Apple scab will also transfer to the fruit, cracking it and causing it to rot.

Before we start discussing how to control Apple scab, we would like to say a few words about how to prevent Apple scab from appearing. Preventing apple scab disease on a site necessarily involves reducing to removing all fallen leaves from the biting area where it can remain infected, and then making sure to cut and burn the wilted shoots and any diseased fruit left on the shoots.

Even before applying harmful chemicals, in specific cases – fungicides, try to treat your precious apple trees in early spring with the fairly safe bio fungicide Bordeaux mixture, and if you can no longer cope with the disease, you can use heavy artillery – fungicides, but be sure to allow and strictly follow the instructions.

When using fungicides, for maximum effect you need to treat before and immediately after flowering. Of course, the use of fungicides, acaricides, etc. requires the use of personal protective equipment – at least – rubber gloves.

Most surprisingly, even fungicides are not always effective against Apple scab, which means that the disease continues to develop after treatment. In this case, additional fertilization of the apple trees could save the situation.

Horticulturists have noticed that a mixture of potassium sulfate, potassium nitrate, ammonium nitrate, and ammonium sulfate is a very good solution to combat infection. All of these are diluted in a bucket of water at room temperature. A bucket of water requires 15 grams of potassium sulfate, 15 grams of potassium nitrate, 10 grams of ammonium nitrate, and 10 grams of ammonium sulfate. With this solution straight from the sprayer, you can treat the plants every 5-6 days and sometimes it can save the trees from Apple scab.


Curled apple leaves may also indicate a lack of nutrients in the soil. For example, if the soil in which apple trees grow has too little nitrogen, the leaves will curl and turn light green. If this problem is not eliminated, the leaves will turn yellow and fall off sooner.

The fastest way to restore a lack of nitrogen in the soil is to apply ammonium nitrate (18-20 grams under the tree, dissolved in water) or to treat the plants with the same amount in the evening. In addition to ammonium nitrate, a solution of urea (0.5%) can be used for treatment; it should also be applied to the tree, especially its leaves, in the evening.

The leaves of apple trees are curled, lacking phosphorus, and have a discolored look; they become somewhat bronze, red, or even purple. Eventually, the leaves will dry out completely and their color will turn a disgusting black. Keep in mind that apple trees on acidic soils are usually deficient in phosphorus if the owner skimps on applying organic matter or does not apply it at all.

The first remedy for apple trees that are curling due to phosphorus deficiency is to add calcium superphosphate. On acidic soils, calcium superphosphate may not help, and here it is best to use phosphate powder. However difficult it may be, you must dissolve the fertilizer as thoroughly as possible in the water, loosen the soil at the roots before application, and moisten and mulch it afterward so that the active substances of the fertilizer do not evaporate in the sun. If the soil is very acidic (pH below 5.0), you can apply potassium monophosphate first and then apply the main fertilizer five days later.

The leaves of apple trees can also curl due to a lack of potassium in the soil, and this curling usually occurs at the same time as their pallor. Potassium-deficient apple leaves will become dull and bluish-green, and their edges will curl downward, which is how you can tell they are deficient in potassium. A little later, a rim forms around the leaves, they begin to dry out, the leaves become emaciated and develop inconsistently, and if the potassium deficiency is not eliminated, the leaves will eventually shrivel.

Interestingly, potassium deficiency occurs most often precisely in acidic soils, as well as if the soil contains for some reason large amounts of calcium and manganese. Potassium deficiency can be remedied by adding potassium sulfate or wood ash to the previously loosened soil in the occluded area. In the case of wood ash, it is important to know that it is a good fertilizer and also contains trace elements, but only 5% potassium, so do not consider wood ash as a primary source of potassium, but rather as a supplementary element.

If the leaves of an apple tree start to curl up rather densely while the growing points start to wilt, this is a sure sign that there is not enough calcium in the soil. Those leaves that do not curl up can quite effectively begin to fall off.

The first remedy for calcium deficiency is the immediate lining of the soil. The nursery circle should be loosened to a depth of 0.8-1.2inch (2-3 cm), two or three buckets of water poured in and 70-100 grams of lime, and a few days later potassium sulfate brought under each apple tree and mulched after applying a layer of humus of about 1 inch on top of it.

Leaf curl on apple trees and the measures involved
Leaf curl on apple trees and the measures involved


Naturally, the leaves of apple trees can curl due to lack of moisture in the soil; if there is too little moisture, the leaves will, among other things, start to dry out.

Remember that in order for apple trees to grow and develop properly, you need to keep the moisture content of the soil in which they grow at 70-75%, and preferably not below or above this level. In fact, it is the substances dissolved in the soil that plants absorb from it in most cases, and without moisture, the absorption of them, alas, will not happen even if they have a lot of substances in the soil. If there is too much moisture, the root tips will begin to rot and the absorption of nutrients from the soil will be disturbed.

Ideally, apple trees should be watered by drip irrigation: the simplest option is a bucket, located under the drainage outlet, at a height – yes, even 20inch (0.5m), where water will flow from the roof into the bucket, protected by a mosquito net, and the bucket will not miss the waste. A hole should be made in the bottom of the bucket, into which a tube with a garden-style drip head should be inserted and placed so that there is a drip head on each bedding strip. As a result, the garden will receive an abundance of water.

When watering manually, it is best to use melted water or rainwater, taking into account natural moisture, i.e. rain (i.e. with or without), and should be watered in the early stages of tree growth (May), during flowering, bud formation, and ovary formation, and during fruit growth. Remember to combine watering with loosening the soil to make it permeable and airy.

In a nutshell. Take care of your plants as if they were children, and then no caprice from their side, especially in the form of curly leaves, will not, and the apple tree will literally fill you with high yields, in addition to all the other things that will also be stable.

Friends, if you have any questions about how to keep the curly leaves on your apple tree, please write them in the comments and we will be happy to answer them, because we may have missed something.

More related information about Garden Pests

Title: The Reasons for leaf curl on apple trees
Source: ThumbGarden
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