Top 7 Apple Tree Diseases and How to Prevent Them Properly

Keeping apple tree diseases at bay is one of the basics when growing this plant in the garden. While some issues are superficial, others may cause deadly damage to your trees.

While growing apple trees is already challenging, dealing with the long list of possible diseases may make you think twice about planting this in your garden.

However, once you can control the issue and keep your apple away from any disease, it must feel so much rewarding.


7 Most Common Apple Tree Diseases and Pests

Diseases that affect apple trees vary from bacterial to fungal infections. Read the following to learn the most common ones and how to control them effectively.

  1. Sooty Blotch and Flyspeck

Sooty blotch and flyspeck usually appear in August or September and are sometimes called the
Sooty Blotch and Flyspeck on Apple

In early autumn or late summer, your apple trees are vulnerable to the attack of sooty blotch and flyspeck. These pests do not cause such huge damage to the plant.

However, they are still capable of shortening its shelf life.

Flyspeck and sooty blotch come as a mixed disease caused by several kinds of bacteria including leptodantium elatius and geastrumia polystigmatis.

If your apple trees experience these diseases, there will be speckles or tiny black blotches on the crop. Even though it does not influence the fruit’s taste, its appearance makes it less appetizing.

You can do the following techniques to treat sooty blotch and flyspeck.

  • Proper pruning and good sanitizing practices will generally help to lower the risk of sooty blotch and flyspeck.
  • Since this fungus prefers high humidity, you should not leave your apple tree too wet.
  • Encourage good air circulation so that the fruit and branches can stay healthy.

Besides, you may also make a homemade solution incorporating bleach and water to control sooty blotch or flyspeck.

Use the mixture to rub the fruit tenderly and take a damp cloth to remove.

  1. The Most Common Apple Tree Diseases

Apple scab is caused by the fungus Venturia inaequalis. It infects crabapples and apples (Malus spp.), mountain ash (Sorbus spp.), pear (Pyrus communis) and Cotoneaster (Cotoneaster spp.).
Apple Scab

Apple scab is the most widespread disease that can affect your tree. If you live in cold, humid climates, you are more likely to experience this issue.

You will notice black lesions on your tree’s foliage and fruit if it gets apple scab infestation. Strange, dark splotches are another symptom of this disease.

In serious cases, the fruits and leaves may fall off prematurely after experiencing unusual color changes. To deal with apple scab disease, you can try the following.

  • Promote healthy circulation through the branches by keeping your apple tree pruned. This can lessen the leaves available to spread the disease.
  • Clear all fallen foliage to diminish the harm of spreading spores.
  • When spring is just around the corner, start applying a commercial fungicide to the apple tree. You can apply it as soon as new shoots emerge twice a month.
  1. Powdery Mildew

Powdery mildew, caused by the fungus Podosphaera leucotricha, attacks buds, blossoms, leaves, new shoots, and fruit of wild and cultivated apples and crabapples.
Powdery Mildew on Apples

Similar to scab, powdery mildew is also one of the frequent apple tree diseases in home orchards. This fungus can attack any part of your plant and may become a severe problem for apples.

Powdery mildew can lessen fruit yields and return yearly when the condition is warm and dry. You will see the emergence of this disease during your apple growing season.

This fungus infects your buds before they open, postponing the blooming stage to several days. Then, once they release, gray or white powder will cover the flowers and foliages.

When it happens, you should not expect fruits since the infected blooms will grow poorly and the leaves curl and fall off.

Here are some efforts you can do to treat powdery mildew in your apple trees.

  • Immediate treatment is necessary when dealing with powdery mildew.
  • When the fungus is still in the buds, use mildew spray to drench the tree regularly. You should follow the procedure with fungicide application.
  • This should help the mildew become less noticeable on new shoots.
  • If you must deal with harsh infections, utilizing a sterol inhibitor fungicide can be a good option.
  1. Cedar Apple Rust

This fungus is wide spread in eastern North America. It is usually associated with rural areas that alternate between farmland and forest or thicket
Cedar Apple Rust

As the name suggests, this disease requires two hosts to reproduce namely an apple and cedar tree. The main culprit of this issue is a pathogen called gympnosporangium juniper-vinginianae.

Young branches are prone to cedar apple rust. You will notice the emergence of lesions on them that widen every growing season.

Unluckily, extensive pruning is the only thing you can do to save your tree from cedar-apple rust. Get rid of all affected produces and dead branches to stop the spread of this disease.

You must clean up the debris to avoid the remaining spores that cause these apple tree diseases to infect your plants again.

Moreover, if you discover any lesions on nearby cedar trees, take them out too. This will interrupt the life cycle of the fungal and minimize the risk of the contagion from coming back.

  1. Bitter Rot

Bitter rot is a common fruit rotting disease of apple (and pear) that occurs in all states where apples and pears are grown
Apple Bitter Rot

Affecting pear and apple trees, bitter rot is a fungal disease that can cause lost fruits. This issue may also infect blueberries, chestnuts, strawberries, and peaches.

Instead of the foliage or branches, bitter rot will target your apple trees’ fruit. Different from most fungi, it can feed through the skin.

You will not notice the infestation of bitter rot immediately since this fungus will stay inactive until the humidity and temperature levels rise.

The dormant bitter rot will break out and become obvious in mid to late summer when the conditions are warm and moist.

Its infestation starts with a tiny brown spot on the fruit skin and grows to get darker rapidly. In serious cases, your apples may drip pink matter via open lesions and dry up eventually.

Although it can be pretty exhausting, here are a few things you can do to treat these apple tree diseases.

  • You must perform the necessary treatment to control bitter rot infection through the whole season since the issue occurs long before it becomes obvious.
  • If you already notice the infection of this fungus, prune the affected bodies immediately and use comprehensive tool sanitation to manage the issue.
  • Preventive measures are the best you can do to avoid problems with bitter rot. Applying fungicide on your apple trees before winter is necessary in this case.

There can be several products available to treat bitter rot, but you must remember that they are not as effective as preventive measures.

  1. Fire Blight

Fire blight is a common and very destructive bacterial apple tree diseases and pears. The disease is caused by the bacterium Erwinia amylovora.
Apple Fire Blight

This bacterial disease can cause severe damage to your apple trees. If you grow particular cultivars like Granny Smith and Jonathan, be prepared with the infection of this disease.

Fire blight develops strongly during spring when the temperatures are hot and humid. Once the dryer summer climates occur, this disease will reduce.

You will not see the symptoms of fire blight until it starts to emerge through openings in the leaves and branches in the spring.

Lesions on the foliages and branches of your apple tree may hint toward this disease. If you notice such issues, try the following tips to treat the fire blight.

  • Similar to bitter rot, the best method to manage fire blight is by performing preventive measures. Prompt pruning and sanitizing are usually effective.
  • Make sure to sanitize your gardening tools with a mix of dish liquid and bleach to prevent the spread of this bacterial disease between branches and trees.
  • Measure 8 to 12 inches of your branches from the noticeable lesions and prune them away before it is too late.

You better refrain from overusing particular bacterial sprays to control these apple tree diseases since it may make your plant develop resistance to treatment.

  1. Apple Tree Bark Diseases

You should immediately prune all the infected parts of the tree and either burn or get rid of this apple tree diseases as quickly as possible. You may spray with sulfur or an appropriate fungicide in the early stages of the disease.
Apple Tree Bark

European Canker and Sappy Bark are among the most common apple tree diseases that are caused by a fungal pathogen.

Both diseases affect the bark of your apple tree, causing trivial to severe damage depending on how early you treat the problem.

Sappy bark makes the infected apple tree bark tinge, decay, and develop a spongy texture. Meanwhile, European canker causes cracked parts and the emergence of papery appearance.

How to Treat Apple Tree Diseases and Prevent Them

Remove dead or diseased branches and dried fruits. Burn or bury all infected plant materials. If you cut down any tree, remove the stump to ensure apple tree diseases do not spread.
Treat Apple Tree Diseases

Of course, it is crucial to monitor your apple trees for infestation and diseases, so you can treat the problems immediately once they occur.

However, there is no necessity to manage any apple tree diseases in the first place. Ideally, you must do any preventive measures to keep your trees healthy and away from issues.

  • To reduce the risk of infection, treat your soil and make sure it is not too low. You can use a test kit to see the pH and apply lime to the garden if the Ph is below 6.0.
  • Refrain from watering your apple trees too often since roots that remain wet for more than one day are more vulnerable to diseases.
  • In 10 days, you just need to water your apple trees once.
  • Find out the right techniques to prune your apple trees and follow them annually. Pruning regularly will improve circulation to healthy fruits and branches.
  • Make sure to maintain the cleanliness of your tools since it can diminish the spread of bacteria from one tree to another.
  • After pruning, do not forget to dip your equipment in a mixture of bleach and water or a 70% alcohol solution.

Finally, by performing the above precautionary measures, you can at least minimize the risk of various apple tree diseases.

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