Apple Scab Is A Fungal Disesase
Apple Scab is a fungal disease that causes severe stress to ornamental crabapple trees. Spores will develop on diseased leaves on the ground. The fungal spores then spread through the air after a rainfall to healthy trees about the time of bud break in the spring. The disease is most prevalent during periods of high humidity in spring and early summer. Once a tree has apple scab, the infection spreads throughout the canopy, re-infecting new leaves all summer long.
What Trees & Shrubs Are Affected By Apple Scab?
The fungus Venturia inaequalis causes apple scab. All non-resistant varieties of the following trees and shrubs can be affected:
- Apple
- Crabapple (Malus spp.)
- Hawthorn (Crataegus spp.)
- Cotoneaster (Cotoneaster spp.)
- Common Pear (Pyrus spp.)
What Are the Symptoms Of Apple Scab?
The signs for apple scab begin to appear in the spring. Brown to olive-green spots appears on leaves and fruit, and these spots spread and darken as leaves start to turn yellow. Leaves may even drop off. The spots on the tree’s fruits may develop into corky, cracked, and rough lesions.
Plant Resistant Trees & Contact Hansen’s Tree Service
The best way to avoid problems with apple scab is to plant resistant varieties of crabapples. Some good choices include:
- M. ‘Prairifire’
- M. ‘Mary Potter’
- M. ‘White Angel’
If a non-resistant crabapple is planted and signs of apple scab appear, implement a strict sanitation policy. Immediately rake and remove all fallen infected leaves to reduce the number of spores available to re-infect the tree and its neighbors. Chemical control applied by professional, trained arborists at Hansen’s Tree Service includes using fungicides to assist with preventing the disease. Multiple applications are made in the early spring after a hassle-free inspection. Keeping the tree as healthy and vigorous as possible will also help to fight off the disease.