July 19, 2023

Crabapple trees are beautiful, especially in the spring when they are blooming, but they can be susceptible to diseases that can cause serious issues and make them look sickly. The tree may be alive, but the leaves and blossoms will look decidedly sparse and discolored. Proper maintenance and vigilance toward any signs of infection can help your crabapple trees stay healthy and blooming well.

White crabapple tree blossom on green leaves background in the garden in spring.

What are the Most Prevalent Diseases of Crabapples?

There are a few diseases that may affect your crabapple trees that you’ll want to be familiar with.

  • Apple Scab

Apple scab can cause scabs to develop on the leaves and fruit of a crabapple tree. These infections usually start early in the spring, and typically appear on young leaves. Initially, the scabs are a light green, but will turn darker over time. This disease is caused by a fungus, so if your crabapple tree receives too much moisture from excess rain, irrigation, or a lack of sunlight, it is more susceptible.

  • Fire Blight

Fire blight is a disease that spreads quickly throughout the tree. This disease will cause the leaves of the tree to appear scorched, as though they had been set on fire. Even after the leaves die, they will not fall off the tree. Reddish lesions can appear on the bark and may ooze a watery, tan liquid. Fire blight can kill the entire tree quickly if it is not addressed right away.

  • Cedar Apple Rust

Cedar apple rust will begin with small green or yellow spots on the foliage, but the spots will enlarge and darken into a rusty color very quickly. The lesions will spread to the fruit, and many trees infected will produce malformed fruit.

How Can I Keep My Crabapple Tree Healthy?

Proper pruning and hygiene are the best ways to keep any plantings healthy. Newly planted trees are far more susceptible to disease, and therefore should be watched carefully for any potential signs of disease. Some homeowners may want to look for varieties of crabapple trees that are more resistant to the most prevalent diseases. For example, Crabapple (Malus species) varieties like ‘Adams’, ‘Callaway’, ‘David’, ‘Dolgo’, and ‘Jewel-berry’ are more resistant to apple scab and fire blight than others.

What Do I Do if My Tree is Showing Signs of Poor Health?

If you notice any of the signs of disease or poor health, you do need to act quickly. For apple scab and cedar apple rust, a fungicide applied to the entire tree as well as pruning any foliage that shows signs of the disease can potentially stop the disease from spreading. Fire blight is much more serious, as it can spread and kill the tree so quickly. In the case of fire blight, hire a tree service to remove any infected parts of the tree, including leaves, fruit, and limbs. In some cases, some of the trunk may need to be removed to save the tree. Your tree service will let you know if the fire blight has progressed too far, and in this case, the entire tree may need to be removed before it spreads to other trees.

The most important step toward keeping your trees healthy is vigilance. If you see signs of infection on the leaves, take care of the problem right away with the correct fungicide and proper pruning. If you are ever unsure of how to handle your crabapple trees, we can help you diagnose and treat the problem. Contact Twin Oaks Landscape to learn more.