7 Common Apple Tree Diseases - Backyard Boss
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7 Common Apple Tree Diseases

While growing and caring for your apple trees is an exciting and rewarding experience, there is always the looming fear of disease. Apple tree diseases are common, and there are numerous different types, but they shouldn’t stop you from harvesting and enjoying the fruits of your labor.

Of all the different types of infections and bacteria, seven main types may target and damage your trees. In this guide, you’ll discover how to identify, treat, and prevent these most common apple tree diseases. It will ensure you know what issues you’re facing and how to deal with them to keep your trees and fruits happy and healthy.

7 Common Apple Tree Diseases

Cedar Apple Rust


Cedar apple rust presents as splotchy bright orange spots on leaves that resemble rust, hence the name. They often appear in mid-to-late spring and cause the fruit to fall off or become deformed.

Cedar apple rust is usually caused by junipers that carry a fungus found in cedar trees. To prevent this infection from spreading, remove any junipers within 200 feet of the tree. Extensive pruning and removing all infected areas is the best way to treat this infection. You should also check nearby cedar trees for the same orange spots and prune them as well.

Apple Scab


A tell-tale sign of apple scab is small olive green or black spots on the underside of the leaves. They can eventually cause leaves to fall off and create tough “scabs” or lesions on the apples, which can cause them to rot or turn brown. It can also result in total foliage loss, which in turn makes the tree susceptible to more diseases.

Treatment for apple scabs includes raking up any fallen leaves and apples to avoid the spread of infection, as well as proper pruning. Once spring arrives, treating the tree with a chemical fungicide biweekly should solve the issue.

Fire Blight


Fire blight causes an apple tree’s twigs and flowers to become shriveled up and turn black, making it easy to identify. The dead leaves, twigs, and flowers remain on the tree as the infection spreads, making the tree look as if it has been scorched or burned by fire.

The best way to treat fire blight is by removing the dead branches and leaves and cutting about 12 inches below any signs of infection. You should also disinfect your pruning tools between each cut to ensure you aren’t spreading infection.

Phytophthora Rot


Phytophthora rot is a fungal infection that can remain dormant in the soil for years. Essentially, it targets the root system first before it reaches the rest of the tree. It usually causes a dark brown coloring that is soft and slimy around the trunk of the tree.

Unfortunately, Phytophthora rot is one of the most difficult diseases to treat. If you do catch it in the early stages, you can try removing the infected soil and roots, allowing the roots to dry out, and replanting the tree.

Powdery Mildew


Powdery mildew is another one of the more common apple tree diseases, and it can affect almost every part of the tree. It can cause buds to delay opening and minimize apple production. It’s easy to identify, though, as leaves and flowers will be covered in a layer of white powder.

If you notice that your buds have powdery mildew, it’s time to act. Spray with mildew spray and fungicide regularly until you can no longer see the mildew.

Bitter Rot


Bitter rot is another fungus that can cause fruit to drop. Unlike many other diseases, it targets the fruit rather than the foliage. It begins as a small brown spot on the skin of the fruit and rapidly grows and darkens, causing the fruit to rot and shrivel.

Bitter rot requires extensive treatment all season long since it does not show any signs before it is apparent. Applying fungicide before the winter is the best way to prevent it. You should also prune any infected branches as soon as possible, cleaning your tools in between cuts.

Sooty Blotch


Sooty blotch is luckily one of the least damaging infections and only affects the appearance of the trees and fruits. It also shortens the shelf life of the apples. Sooty blotch appears as dark grey blotches on the fruit, though they do not affect the flavor or texture.

Sooty blotch is treated with pruning and sanitizing, like many other infections and diseases. This will improve circulation and reduce the risk of bacteria forming. You can treat Sooty blotch with a mixture of one-ounce bleach and one gallon of water, dabbed lightly on any affected areas.

How to Prevent Common Apple Tree Diseases

Apple Trees
Image credits: Slatan via Canva

While identifying the disease could technically be labeled the first step in targeting apple tree diseases, there are a few things that will help you combat them before they ever begin.

Some apple cultivars are disease resistants, such as Enterprise, Goldrush, Liberty, and Red free. By choosing one of these options, your tree will be less likely to become infected. Regular pruning and cleaning tools can help your trees stay healthy and disease-free.

Overwatering can also cause your trees to become more susceptible to disease as the roots can become damaged and weakened. You should water apple trees once every 10 days unless it rains.

In Summary

Homegrown apples will always look different from the fruits you’ll find in a grocery store. It means they will have imperfections, varied coloring, and will rarely be “perfect” in appearance. But diseases are different in appearance and shouldn’t be too hard to spot.

While your apple trees may be faced with disease, you don’t have to lose your harvest. You can treat diseases as long as you know the signs and how to handle them. You can prevent them using the tools and tricks outlined in this guide, so you never have to struggle against apple tree diseases.

Apple trees require care and attention to produce the best quality fruits. Check out this guide on how to prune an apple tree to ensure you get the best harvest every year. While identifying the disease could technically be labeled the first step in targeting apple tree diseases, there are a few things that will help you combat them before they ever begin.

Did any of these tips work for you? Let us know in the comments below!

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