What Are the Big Fat Bubbles on a Cedar Tree Leaf?

Cedar Apple Rust

• Cedar apple rust is a fungal disease that causes big or fat bubbles to form on the leaves of the cedar tree. The disease possesses a lengthy lifespan of two years.

The Bubbles

• The bubbles on the cedar leaf first appear as small, yellowish spots, which eventually become larger and redder in color around the border of the bubble. Inside the bubble a tiny, black spot emerges. A series of tiny hairs grow from the inside of the bubble with leaf tissue surrounding it, giving the bubble a cup-like appearance.

Galls

• The cup-like bubble is known as a gall. The gall develops a chocolate or brown color during the winter. In the spring, the gall grows two orange horns. Fungal spores that spread the disease are distributed throughout the horns.

Management

• Damage caused by cedar apple rust is cosmetic and rarely threatens the overall health of the cedar tree. The usual recommended treatment involves picking the galls off the tree. Fungicides may be utilized but only for severe infections.