Diseases
Apple Scab
Unsightly spotting, yellowing leaves, and early defoliation on apple and crabapple trees can be a sign of apple scab. Here is what to watch for, what may be driving the infection, and how My Arborist can help protect valuable landscape trees.
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On this page
What is it?
Signs & symptoms
What causes it
Trees affected
When to act
How we help
Prevention tips
FAQs
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Overview
What is Apple Scab?
Apple scab is a fungal disease that affects the leaves, fruit, and young twigs of susceptible trees. It is especially common on apple and crabapple trees and is often first noticed when olive-green to brown spots begin showing up on new foliage. While the disease is often known for its ugly appearance, repeated infections can do more than hurt curb appeal. Ongoing defoliation can weaken the tree over time and make it more vulnerable to other stresses.
When you'll see it in Michigan
Jan
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Overview
Common signs & symptoms
Check each one you're seeing on your tree — your match strength updates below.
Root Cause
What Causes Apple Scab?
Apple scab develops when fungal spores infect new tissue during wet spring weather. Moisture, extended leaf wetness, and poor air circulation all create conditions that make infection more likely. Once the disease gets established, symptoms can continue to build through the season. Because it tends to return year after year, waiting too long often turns a manageable issue into an ongoing cycle.
Plants at Risk
Trees commonly affected
Apple scab is most commonly found on ornamental crabapples and apple trees, but related species such as hawthorn and pear may also show symptoms. Properties with dense canopies, overhead moisture, or a history of repeat infection often see the most noticeable damage.
Red Flags
When Should You Act?
If a tree shows minor spotting once and otherwise stays healthy, monitoring may be enough at first. But if leaves are dropping early, fruit is being affected, or the same tree struggles with the problem year after year, it is a good idea to bring in an ISA Certified Arborist. Early identification matters because properly timed preventive treatment is usually more effective than reacting after the disease has spread.
Our Approach
How My Arborist helps
My Arborist starts with a professional evaluation to confirm that apple scab is the real issue and not another problem with similar symptoms. From there, our arborists can recommend a customized plan based on the tree, the severity of the infection, and the season. Solutions may include disease-control spray timing, trunk injection strategies where appropriate, and overall plant health support to reduce long-term stress.
01
Disease evaluation
Confirm the diagnosis before treating
02
Customized plan
Based on the severity of the infection and season
03
Disease control
Timed spraying and truck injections
04
Plant health support
Improve vigor and reduce susceptibility
Stay Ahead
Prevention tips
Improve air flow with proper pruning when appropriate
Avoid letting repeat infections go untreated year after year
Support tree health with proactive care and monitoring
Pay close attention during cool, wet spring periods
Common Questions
Frequently asked questions
What does apple scab look like?
Apple scab usually appears as dark or olive-colored spots on leaves and fruit. Over time, infected leaves may yellow and fall early.
Is apple scab only cosmetic?
Not always. A single infection may be mostly aesthetic, but repeated defoliation can weaken the tree and make it more susceptible to other problems.
Can apple scab be treated?
Yes. Treatment is often most effective when it is timed preventively and built around the season, weather conditions, and the severity of the issue.
Should I remove infected leaves?
Cleanup can help reduce disease pressure, but sanitation alone usually is not enough if the tree has an ongoing history of infection.
Keep Exploring
Related tree diseases
Oak Wilt
Leaves brown from the margins inward
Anthracnose
Fungal disease most noticeable in spring
Needle Cast
Evergreen Needle Disease
CONSULTATION
Not sure what is causing the problem?
My Arborist can inspect the symptoms, identify likely stressors, and recommend the right next step.
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