Apple Scab

Apple Scab

Apple scab is a serious fungal disease of ornamental crabapple and apples, and can be observed on hawthorn, mountain-ash, cotoneaster and common pear. Scab is observed on the leaves, blossoms, fruits and sometimes on young shoots. Commonly in spring and early summer, leaves will develop small brown to olive green spots that will enlarge and darken, often becoming circular in shape. Numerous infections on the leaf will cause leaves to distort, yellow and drop prematurely. Seasons with abundant moisture in spring and summer will increase the severity of the disease. Though it is not a tree killer, yearly infections can weaken a tree making it more susceptible to other insect or disease issues.

How to Identify Damages Caused By Apple Scab

Early Signs

  • Small olive green to brown spots on the upper leaf surface in spring / early summer.
  • Twisted and puckered leaves that have black, circular scabby spots.

Late Signs

  • Leaves with areas that are dark brown to black, often distorted, yellowing, and falling off the tree prematurely.
  • Oftentimes scabby spots fuse and cover the whole leaf.

Apple Scab Prevention

For Homeowners

  • Plant varieties that are more resistant to apple scab
  • Plant crabapple and apples in full sun with good air movement.
  • Avoid planting crabapple / apples in shade or in areas of poor drainage.

Apple Scab Prevention

For Professionals

  • Plant more resistant varieties.
  • Proper pruning to improve structure and disease management
  • Upon planting, spread a layer of compost along with 2 to 4 inches of organic mulch over the root zone

Apple Scab Treatment

Spray the proper fungicide at the right time for disease management. 2-3 times per season.

Apple Scab FAQs

Can I have my tree sprayed after I observe symptoms?

No, sprays need to be applied early before symptoms are present.

What are the patchy greenish growths growing on the trunk? Is that apple scab?

No, those are lichens, not related to apple scab, they are harmless.