Apple Scab is a fungal disease

Apple Scab is a fungal disease that causes serious stress to ornamental crabapple trees. Spores will develop on diseased leaves on the ground. The fungal spores are then spread through the air after a rainfall to healthy trees about the time of budbreak in the spring. The disease is most prevalent during periods of high humidity (spring and early summer). Once a tree has apple scab, the disease spreads throughout the canopy; re-infecting new leaves all summer long.

✓ What trees and shrubs are affected?

All non-resistant varieties of

  • Apple
  • Crabapple (Malus spp.)
  • Hawthorn (Crataegus spp.)
  • Cotoneaster (Cotoneaster spp.)
  • Common Pear (Pyrus spp.)

✓ Symptoms

The signs for apple scab begin to appear in the spring. Brown to olive-green spots appear on leaves and fruit. The spots spread and darken as leaves begin to turn yellow. Leaves may even drop off. Spots on the fruits may develop into corky lesions.

✓ Solution

The best way to avoid problems with apple scab is to plant resistant varieties of crabapples!!! Some good choices are: M. ‘Prairifire’, M. ‘Mary Potter’ and M. ‘White Angel’ If a non-resistant crabapple is already planted and signs of apple scab appear, implement a strict sanitation policy. As infected leaves fall from the tree, rake and remove them immediately. This will reduce the number of spores available to re-infect the tree. Keeping the tree as healthy and vigorous as possible will also help to fight off the disease. Chemical control includes using fungicides to assist with preventing the disease. Multiple applications are made in the early spring. – See more at: