Apple Tree Diseases & How to Cure Them

Juicy, delicious, and crisp to bite into – apples are a widely enjoyed fruit around the world for their nectar-sweet and tangy flavor. Unfortunately, growing apples can be a challenge, mainly because of common apple tree diseases. 

Apples belong to the rose family (Rosaceae) which is particularly vulnerable to a host of different diseases. Depending on where your apple tree is being grown, the kind of weather conditions it is exposed to, the soil it has access to, and whether or not it is being adequately cared for, can determine if your apple tree will fall prey to disease.

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How To Identify Different Types of Apple Tree Diseases 

Fortunately, it is easy to identify if your apple tree is suffering from an infection. Identification is the first step in helping your apple tree battle against infection, and recover quickly to become healthy again. To help you identify what disease is affecting your apple tree here is a list of the four most common diseases that can help you figure out what to do if you notice your plant showing symptoms of an ailment:

Apple Scab 

Apple Scab Apple scab is a fungal infection that is caused by the spores of a hemi-biotrophic fungus (Venturia inaequalis) being carried by wind, rain, or the bodies of animals until they come in contact with your plant. Check the undersides of the leaves for symptoms of apple scab. If you notice yellow-brown lesions, then your apple tree may be suffering from this fungal infection. At first, scabs will be seen as small yellow or brown bumps on the infected leaves. However, as the infection spreads, these areas may turn dark brown or even black due to dying plant cells. 

Don’t wait for the infestation to worsen, and take action to help your plant immediately. Spray your apple tree with liquid copper soap and sulfur-based fungicide when you notice symptoms. Continue to do so at 7 (wet weather) or 10 (dry weather) day intervals until your apples are ready to be harvested. It is also recommended to rake the leaves that fall off your apple tree to prevent further dispersal of spores.

White Rot

White Rot on Branches Apple trees being grown in the southern climate may be prone to white rot infection. This plant disease is caused by Botryosphaeria dothidea, a dangerous fungal pathogen. Your apple tree is suffering from a white rot infection if you notice reddish-brown blisters on the trunk, branches and fruit. The white rot doesn’t affect the leaves of your plant. 

To treat your apple tree, begin by getting rid of the fruit infection as soon as you detect it. Next, you will want to prune your apple tree and remove diseased limbs from the fruit tree to give it the best chance of healing quickly.

Powdery Mildew

Powdery mildew is another fungal infection that is easy for most plants to contract, especially during moist weather. The warm and humid environment provides the Podosphaera leucotricha fungal spores the ideal opportunity to germinate and infect your apple tree. As the name suggests, your apple tree is experiencing powdery mildew if you notice a coat of white powder freckled across the surface of the plant. You may also notice your plant’s leaves curl up and become stiff.  Apple tree leaves with white powdery mildew infection
While not deadly at all, powdery mildew weakens your apple tree and can lead to blossoms falling off prematurely. Fungicides such as sterol inhibitors (myclobutanil and fenbuconazole) are exceptionally effective against powdery mildew. Potassium-bicarbonate sprays every two weeks are also useful in fighting powdery mildew.

Cedar Apple Rust

Cedar Apple Rust If your apple tree has been planted close to certain species of juniper or red cedar, it is possible for it to catch cedar apple rust fungus. This disease is contracted when you plant juniper or red cedar varieties (in close proximity to your apple tree) which can act as hosts for the Gymnosporangium clavipes fungus to spread its spores and infect your plant. Your plant is suffering from cedar apple rust if you observe rusty golden-brown spots on your apple tree’s leaves.

Both hosts need to be close to each other for the disease cycle to continue, so your first step should be to separate the two. Follow this up by removing diseased branches, and applying fungicide to the trunk, branches, and foliage.