Crabapple Tree Diseases And Pruning Diseased Trees

Posted on: 26 December 2014

If your flowering crabapple tree has dark spots or its leaves are falling prematurely, your tree has a disease. Below you'll learn about common crabapple tree diseases and how you can prune your tree back to health.


This fungal disease thrives during wet weather and cooler temperatures. The first indication of apple scab is dark colored spots on the leaves. As the fungus progresses, a fuzzy substance will appear on the leaf stems and foliage. When the disease attacks the surface of the fruit, you'll notice the presence of round bumpy spots.

As the leaves turn yellow and wilt, they'll fall to the ground. By the middle of summer, a large percentage of the leaves will be gone and the tree will appear puny.

Fire Blight

This crabapple tree disease affects the flowers, leaves and branches of the tree. Blisters appear on the stems and pus may seep out of older lesions. The end section of infected branches will curl and turn dark brown or black.

As the lesions grow larger and infect thick branches, the disease will spread into the trunk of the tree. As the disease kills the flowers and leaves, they'll stay attached to the tree.


Even though crabapple trees can grow as tall as 30 feet, they're susceptible to canker disease when they're stressed due to insufficient water. When your tree has canker, the wood beneath the bark will have a brown hue. Another indication is black bumps on the leaves, right before they wilt.

During dry weather conditions, water your tree every two weeks. Saturate the ground around your tree with four to six inches of water to keep canker away.

Frogeye Leafspot

Dark spotted leaves with purple edges signify frogeye leafspot. As the disease progresses, the spots will turn gray and form a circular pattern. Finally, the leaves will turn yellow and fall from the tree. To prevent this fungus from attacking your trees next season, pick up the wilted leaves and burn or bury them away from your trees.

Pruning Diseased Trees

When you first notice a diseased crabapple tree, grab your pruning shears to cut off the unhealthy branches. This keeps the disease from spreading to the healthy areas of the tree and stealing nutrients.

To determine the health of the branch, carefully peel off a piece of the bark and examine the color underneath. If you see a white or green hue, the branch is healthy. If the color is brown or black, the branch is dead and you should remove it. If the branch has buds, it's healthy, so you won't need to do the bark test.

Follow these tree trimming tips when dealing with a diseased crabapple tree.

  • If the branch has cankers, make your cut at least 6 inches above the lesion. This will ensure that you've removed the entire diseased area around the canker.
  • Prune your trees when the weather is dry because the microbes can spread to healthy leaves easier when the leaves are wet.
  • Submerge your shears into a mixture of bleach water for 15 seconds after each cut to prevent the spread of the disease. Clean the shears thoroughly in the solution after you're done.
  • After pruning your infected crabapple tree, wash your gloves and clothing. This will remove any pathogens that have traveled through the air and landed on your clothes.

When planting new crabapples trees, purchase varieties that are resistant to scab and fire blight. Disease resistant cultivars include Adams, Callaway, David, Dolgo and Jewelberry.

If your crabapple tree has a disease, now you can identify the pathogen and trim off the diseased areas to keep it healthy. If you're unable to prune your tree, contact a company that performs tree trimming to do the job for you.