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

Apples might just be the world’s most popular fruit. They’re a favorite in many gardens because they’re not too fussy about where they grow. However, it’s not just us humans who love apple trees; a bunch of pests and diseases are also keen to get a piece of the action.

When it comes to apple tree leaves curling up, the usual suspects are pests, fungal infections, not enough water, or not feeding the tree right. To sort out those twisty leaves, you can give the tree a good spray with horticultural oil. Make sure to water the tree when the top 2-3 inches of soil are dry, and feed it a multi-purpose fertilizer twice a year. That should do the trick!

1. Pests

Apple tree leaves curling because of aphids.

Apple tree leaves curling because of aphids.

Aphids are one of the most common pests that bother apple trees. These tiny bugs like to hang out on young stems and under leaves, where they feed off the tree’s sap. This can cause the leaves to curl outward or even fold along their length.

Leaf rollers are another pest to watch out for. They lay eggs on the leaves, and when the larvae hatch, they roll the leaf up to create a cozy home. Inside this rolled-up leaf, the larva munches away, growing into a full-sized insect.

Here’s what you can do:

  1. Spray your apple tree with a water-based horticultural oil solution. This helps manage these pests without harsh chemicals.
  2. Try to avoid using pesticides. They can be harmful to the environment and other beneficial organisms.
  3. If you spot leaf rollers, simply remove the affected leaves where you see them rolled up. This can help stop the larvae from developing further.

2. Fungal and Bacterial Diseases

Apple tree leaves curling because of apple scab.

Apple tree leaves curling because of apple scab.

Twisted apple leaves can often be a sign of disease, just as much as pests. One major disease is apple scab. It affects the leaves and fruits, causing large brown spots. The leaves can become heavily deformed, twisting or folding.

Another disease to watch out for is powdery mildew. This shows up as a white coating on leaves, leading to their deformation. The leaves might turn saucer-like or wavy, and sometimes even change color to dark brown or black.

Then there’s fire blight, a serious bacterial disease. It can really harm apple trees, often preventing them from bearing fruit. If left unchecked, it can even spread to other fruit trees.

Here’s what you can do:

  1. Use a fungicide to treat both apple scab and powdery mildew.
  2. Remove and burn any leaves that are severely damaged. This helps prevent the spread of the disease.
  3. After some time, spray the tree again to ensure the diseases are kept at bay.

3. Inadequate Fertilization

Apple tree leaves curling because of improper fertilization.

Apple tree leaves curling because of improper fertilization.

If your apple tree’s leaves are curling, it might be because the tree isn’t getting enough nutrients. Sometimes, even if the minerals are in the soil, the tree can’t absorb them properly, especially if the soil is too alkaline. In alkaline soil, the roots struggle to take up nutrients, leading to a condition called chlorosis. You’ll notice not just curling leaves, but also a yellowing of the leaves.

Here’s what you can do:

  1. Check and adjust the soil’s pH around your apple tree. Apple trees thrive best in soil with a pH of around 6.5.
  2. Use a slow-release, multi-purpose fertilizer specifically designed for trees.
  3. Fertilize once early in the spring (around March-April), and then again in the middle of summer.

4. Scorching Sun

Apple tree leaves curling because of scorching sun.

Apple tree leaves curling because of scorching sun.

Sometimes, too much sun can make apple tree leaves curl. This is more common in young trees that don’t have a fully developed root system yet. Older, established trees usually don’t have this problem.

You might also notice the leaves turning brown or shriveling up. If it gets really bad, the leaves might even start to fall off.

Here’s what you can do:

  1. Create some shade for your apple tree, especially if it’s a younger one. This can protect it from the harsh sun.
  2. Water your apple tree well. A generous amount of water will help it cope with the intense sunlight and heat.

5. Lack of Water

Underwatering

Apple tree leaves curling due to underwatering.

Dehydration is a really common reason why leaves curl in many plants, especially when the weather gets hot. The tree tries to cool itself down by evaporating more water, and if there isn’t enough moisture in the soil, the leaves start to shrivel and curl, usually beginning at the tips.

Here’s what you can do:

  1. Check the soil around the tree. If the top 2 to 3 inches of soil are dry, it’s time to water the tree.
  2. Give your apple tree plenty of water. You want the soil to be moist but not waterlogged.
  3. In the future, try not to let the soil dry out more than 2 to 3 inches deep.
  4. Opt for deep watering rather than shallow, frequent watering. This encourages deeper root growth.
  5. Mulch around the tree with compost. This helps retain moisture in the soil.

6. Overwatering

Overwatering

Apple tree leaves curled because of overwatering.

If your apple tree gets too much water and the drainage isn’t good, the roots can start to suffer. First, they don’t get enough air, and then, root rot can set in. This means the leaves don’t get enough water, and the sun can make them curl up.

Here’s what you can do:

  1. Cut back on watering. You don’t need to water the tree too often.
  2. Wait to water the apple tree until the soil around the roots dries out to about 2 inches deep.
  3. Work on improving the soil’s drainage. This helps prevent water from building up and causing root problems.