Apple Scab – What Is It and What Should I Do?

Apple scab is one of the most common tree diseases. It is caused by a fungus called Venturia inaequalis. While it mainly targets apples and crabapples, it can also affect other fruit trees like pear, cotoneaster, and mountain ash.

One of the signs that your tree has this disease is that the leaves develop olive green or yellow spots on the surface and dark spots underneath. One way to prevent this disease is to actually plant apple varieties that are scab-resistant, including Priscilla, Pristine, Crimson Crisp, and Winecrisp. If your tree already has the disease, you can still use a fungicide or spray to treat the fungus.

Apple scab is a disease that targets fruit trees, mainly apples and crab apples.

The fungus Venturia Inaequalis is the reason for apple scabs. Aside from apples, and crab apples, it can also affect other fruit trees like mountain ash and pear. While it may look unsightly, this disease will not kill your tree. Instead, it will cause discoloration on the leaves and fruits. The tree may become weaker, which will make it more vulnerable to injuries during the winter, plus decreased bloom.

During winter, the fungus spends its time on the affected leaves that have fallen from the trees. By springtime, the spores spread to other healthy trees through wind and irrigation.

Leaf spots will appear on trees that have apple scabs.

Tree leaves badly damaged with apple scab disease near Littleton, CO.

There are several ways to identify if your tree is infected with apple scabs. According to Spruce, the first sign is usually olive-green spots found on the underside of the leaves. This will turn black or brown in color, and it feels like velvet when touched. The leaves can also become twisted before falling prematurely.

The fruits will also have scab-like spots, which can cause them to become misshapen. Although it will affect how the fruit looks, the fruits are still safe to eat.

There are many ways to prevent it from spreading from one tree to another.

One of the best tips is actually to plant trees that are resistant to scabs. This includes Priscilla, Winecrisp, Pristine, Crimson Crisp. If that is not possible, there are still other ways to prevent it, including:

  • Destroying any infected leaf that has fallen – You want to stop the disease from spreading, and the leaves house the spores that can spread to other trees.
  • Keep your trees pruned so that there is enough space between trees -This allows for better air circulation, and the leaves will dry faster, preventing the spores from germinating.
  • When watering, try to keep the water away from the leaves and fruits – You might also want to do the watering during the early morning so that the leaves will be able to dry out quickly.

Applying fungicide will help put the fungus to rest.

Fungicide can be applied to healthy trees to prevent them from getting the disease. The fungicides are usually sprayed sometime in spring, just as the bud is starting to grow. But applying them to infected trees will not have any effect.

Take note that fungicides cannot be applied to trees that are resistant to scab. There are many types of fungicides, so it’s important to know what to put and when to put it.

Need a tree care specialist to handle this problem for you? Call  (970) 465-2474 today.

Here at Tree Keepers, we have a comprehensive tree and shrub care program for property owners in Littleton, Golden, Broomfield, and surrounding areas in Colorado. You can be assured that we will only offer quality service, starting from diagnosis to treatment. All our licensed arborists are experts, knowledgeable, and always keeping up to date with information.

Call us at  (970) 465-2474 to keep diseases away from your trees and shrubs, or if you want them treated for any apple scab or other diseases.

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