Gymnosporangium clavipes

Gymnosporangium clavipes is a species of fungus in the family Pucciniaceae. It is commonly known as the Cedar-Apple Rust due to its unique life cycle involving two hosts: the Eastern Red Cedar (Juniperus virginiana) and the apple tree (Malus domestica).

Description

The Gymnosporangium clavipes fungus is characterized by its distinctive orange, gelatinous telial horns that appear on infected cedar trees during wet spring weather. These horns produce teliospores which are then carried by wind to infect apple trees. On the apple tree, the fungus causes yellow spots and cankers on the leaves, fruit, and twigs.

Life Cycle

The life cycle of Gymnosporangium clavipes is complex and involves two different hosts. The fungus overwinters as a gall on cedar trees. In the spring, during wet weather, these galls produce orange, gelatinous telial horns. These horns release teliospores which are carried by the wind to apple trees. Once on the apple tree, the teliospores germinate and infect the tree, causing yellow spots and cankers. The fungus then produces aeciospores which are carried by the wind back to cedar trees, completing the life cycle.

Control

Control of Gymnosporangium clavipes involves a combination of cultural practices and chemical treatments. Cultural practices include removing galls from cedar trees and avoiding planting cedars near apple orchards. Chemical treatments include the application of fungicides to apple trees during periods of high disease pressure.

Impact

The Gymnosporangium clavipes fungus can cause significant damage to apple orchards, particularly in regions where Eastern Red Cedar is common. The disease can reduce the yield and quality of the apple crop, and in severe cases, can cause tree death.

See Also

• Gymnosporangium juniperi-virginianae
• Cedar-apple rust
• Pucciniaceae