Cedar Apple Rust: A Fungal Disease Affecting Apple Trees and Red Cedar
Introduction
If you’ve noticed strange, green-brown growths on your cedar tree or have a poor apple crop, you may have a fungal disease called cedar apple rust. While this disease can cause more damage to apples than cedar trees, it’s important to know how to prevent it from happening in the first place.
What is Cedar Apple Rust?
Cedar apple rust (CAR) is a unique fungal disease that affects both apple trees and red cedar trees. Spores from one type of tree can only infect the other type. For example, spores from apple trees can only infect cedar trees, while spores from cedar trees can only infect apple trees. This disease can quickly cause apple trees to lose their leaves and cause blemishes on the fruit.
Signs of Cedar Apple Rust Disease
- Cedar Trees:
- Large, brown growths called cedar apples
- Small, greenish brown galls on the upper and inner foliage in summer
- Apple Trees:
- Small, greenish yellow spots on the leaves that gradually turn orange-yellow or rust colored with a red band
- Cup-like lesions on the undersides of the leaves and on the fruit, causing malformation
Life Cycle of Cedar Apple Rust
The CAR fungus spends the winter inside the cedar apples. In the spring, when it rains and the apple trees are blossoming, the cedar apples start to grow gelatin-like tendrils called telia. These telia produce spores that travel through the air and land on apple trees. If there is enough moisture, the spores will germinate and infect the apple trees within one to two weeks. The cycle then continues back and forth between the cedar trees and apple trees.
Control Methods for Cedar Apple Rust
- Prevention:
- Remove cedar apples from cedar trees before they reach the telia stage by pruning them off in late winter.
- Remove any red cedar trees within a two-mile radius of your apple trees.
- Plant resistant apple varieties.
- Chemical Control:
- Use cedar apple rust fungicides. Apply them periodically during the pink stage of apple bud development and continue throughout the season to protect new leaves and developing fruit.
Additional Tips
- Check with your local extension service for specific fungicide recommendations and application schedules.
- If you have a large number of cedar trees, it may not be practical to remove them all. In this case, using fungicides may be your best option.
- Remember, cedar apple rust is a fungal disease that can be prevented and controlled with proper management practices. By following these tips, you can help keep your apple trees healthy and productive.
