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6 Causes of Apple Tree Leaves Curling (And How To Fix Them)

Apples are probably the most common fruit on earth. Thanks to their unpretentiousness, apple trees occupy a place of honor in the gardens of a large number of gardeners. But there is a whole horde of pests and diseases that also want to profit from your apple tree.

Aphids, fungal diseases, lack of water in drought, or improper feeding are the major causes of curling apple tree leaves. To fix twisted leaves wash the aphids off with water or spray the apple tree with horticultural oil. Also, water the tree when the soil is 2-3 inches dry and fertilize it twice a year with a multi-purpose fertilizer.

Pests are the major cause of curling apple tree leaves

Apple tree leaves curling because of aphids.

Apple tree leaves curling because of aphids.

Aphids are small bugs that settle on young stems and the underside of leaves. They have a parasitic way of life, sucking the sap of the apple tree.

As a result of their life activity, leaves curl outward or collapse along their length.

These insects are easy to spot because they are often spread by ants. In addition, their colonies are quite large and conspicuous.

To get rid of the aphids, you can wash them off with a hose. But this is convenient if the apple tree is small or the spread of pests is insignificant. If the tree is large enough, you need to spray it with an aqueous solution of horticultural oil. Avoid using pesticides!

To prepare the solution properly, dilute 3 teaspoons of soap in 1 gallon of water. Then add 5 tablespoons of horticultural oil (Neem oil) and shake the mixture well. Spray all the leaves thoroughly, especially the lower part of the leaves. Repeat the spraying if it doesn’t have the desired effect.

Another type of pest is leaf rollers. These insects lay eggs on leaves and when larvae emerge, they roll up the leaf. In this roll, the larva will develop into a full-grown insect by eating the leaf.

You can simply remove the curled leaves if there are few. Don’t leave the removed leaves in your yard, rather burn them or throw them away as far away as possible. Or simply squash them.

If the spread of leaf rollers is large, then spray the apple tree with horticultural oil.

Fungal and bacterial diseases

Apple tree leaves curling because of apple scab.

Apple tree leaves curling because of apple scab.

Diseases are no less common causes of twisted apple leaves than pests. Their number is large enough and it makes no sense to list them all, so I will tell you about the most frequent ones and you will learn what to do in each particular case.

The first serious disease is apple scab. It affects both the leaves and the fruits, resulting in large brown spots on them. The leaves become considerably deformed, twisted, or folded in two.

The second disease is powdery mildew. Symptoms of the disease are white coating and deformation of leaves. Leaves become saucer-like or wavy. In addition, the color may change to dark brown or black.

For both diseases, fungicides or copper-containing products are most effective. Also, remove severely damaged leaves and burn them. Never make compost from leaves affected by scab! From now on, keep the garden clean and well ventilated.

The last of the diseases go fire blight. This is a fairly serious bacterial disease that causes significant damage to apple trees. A tree infected with this disease rarely bears fruit and if you do nothing, the disease can spread to other fruit trees.

Symptoms of this disease are curled and droopy leaves, then they turn brown and fall off. There are no effective treatments yet, some results can be achieved using copper sulfate and Bordeaux mixture and antibiotics. Trees infected with this disease are usually removed.

Inadequate fertilization

Apple tree leaves curling because of improper fertilization.

Apple tree leaves curling because of improper fertilization.

Lack of nutrients can also cause the leaves of an apple tree to curl. This can be explained by the fact that the tree loses a lot of energy to produce fruit, and if it is not fed next year, the leaves can become deformed.

Apple trees can suffer from a lack of minerals, not only because they are not near the roots, but also because the soil is too alkaline. In alkaline soil, most nutrients are very poorly absorbed by the roots. This leads to a disease called chlorosis. The leaves not only curl, but they also turn yellow.

The first thing you need to do is to acidify the soil around the tree. The ideal pH for apple trees is 6.5. To achieve this value, mulch the surface under the crown with compost, but do not cover the trunk of the tree.

The compost must be of good quality, which means that it must be made from the pathogen-free plant material and with access to air. It should also be free of food scraps. If you do not know how or do not want to make compost, buy it in a garden store. Choose a quality product from a reputable manufacturer.

Next, you need to fertilize your apple tree properly. I recommend using a multi-purpose tree fertilizer with all the necessary trace elements and with a balanced NPK formula.

If you can find the fertilizer in slow-release pellets, that would be ideal. In that case, you will only need to fertilize once in early spring (March-April) and a second time in mid-summer.

Scorching sun

Apple tree leaves curling because of scorching sun.

Apple tree leaves curling because of scorching sun.

Too much sun can sometimes cause leaves to curl. In most cases, this happens in midsummer when there are no cloudy days for a long time. It is also possible that the leaves have unfolded in partial sunlight, but then a hot and sunny time has arrived. As a result, the leaves curl up to reduce their area and get less sunburn.

This rarely happens in large and already established apple trees. Young trees with an undeveloped root system are most susceptible to the sun. Also, potted apple trees often suffer from excessive sun exposure.

Other symptoms can be browning or shriveling of foliage. Eventually, the leaves will fall off.

To help the tree survive the harsh sun you need to provide some shade. If the apple tree is growing in a pot, move it to a place where the sun will only shine for the first half of the day. This can be near the east wall of the house.

If the apple tree is growing in the ground, create some shade on the west side. You can use a garden umbrella or something similar. A good solution is to install a shade net. I very often use a shade net for my newly planted plants.

But remember that sooner or later you have to take the shade out because the apple tree is a sun-loving plant. For good fruiting, it needs at least 8 hours of sunlight per day during the growing season.

Lack of water in drought


Apple tree leaves curling due to underwatering.

Dehydration is a very common cause of leaf curl in so many plants. As in the previous case, it happens most often in hot weather. It increases the amount of water evaporated to cool down, and if the ground is not wet enough, the leaves will shrivel and curl starting at the tips.

Again, young unrooted and potted apple trees are most susceptible to drought damage. A mature apple tree with a branched root system can provide itself with water in any weather.

If your apple tree’s leaves are deformed, stick your finger in the soil near the tree. If the ground has dried out more than 2 to 3 inches, it could be due to a lack of water. Water the apple tree with plenty of water to make the ground around it moist but not swampy.

In the future, do not let the soil dry out more than 2 to 3 inches. Use deep watering instead of shallow and frequent watering.

In pots, the soil dries out in a much shorter amount of time than in the garden. So if you practice growing apple trees in a container, check the soil moisture every day and water the apple tree when it starts to dry out.

Also, mulch the surface of the tree with compost. I’ve already talked about this above. But in short, the compost must be of high quality and professionally prepared. The layer of mulch should not be more than 2-3 inches thick. There should be a gap of at least 1-2 inches between the mulch and the trunk of the apple tree.

Overwatering and root rot


Apple tree leaves curled because of overwatering.

With too much water and poor drainage, the root system begins to fail. The first thing that happens is that the roots do not have enough air, the second is that root rot begins. All this leads to the leaves not getting enough water and the sun causes them to curl.

The symptoms of overwatering are very similar to the symptoms of underwatering because in both cases the roots are not giving water to the leaves. Additional signs are yellowing or browning of the leaves.

If the soil in your apple tree has been wet for a long time and the leaves are deformed, overwatering may be the cause.

To remedy the situation, stop watering frequently or move the water away from the tree, depending on what is causing the overwatering. If, for example, water from the roof leaks under the apple tree, divert it with a gutter to the other side.

Water the apple tree no sooner than the soil around the root system is about 3 inches dry.

Also, you need to improve the drainability of the soil. In clay, soil water likes to stay for a long time, which can lead to root rot. If the apple tree is growing in a pot, or if it is still young, transplant it into soil rich in organic matter (compost). If the apple tree is already large, it will most likely be able to recover from overwatering after a while.

Key Takeaways:

  • Various insects can cause the leaves of an apple tree to curl. Spray the plant with horticultural oil.
  • Apple scab and other diseases cause leaf curl. Spray the apple tree with a fungicide and remove any damaged leaves.
  • Inadequate or improper feeding can cause deformed leaves. Fertilize the apple tree at least twice a year with a multi-purpose fertilizer.
  • The scorching sun and lack of moisture in the soil are common causes of curled leaves. Water the apple tree when the soil is 2 to 3 inches dry.