Infected leaves may remain on the tree or may become yellowed and drop. They are somewhat like leaf lesions but much larger and often cause fruit to become disfigured or to develop unevenly. Light brown to reddish brown galls form on the branches of red cedar. The galls' surfaces are covered with depressions much like those on a golf ball. Disease cycle Spores discharged from these gelatinous telial horns on red cedar are easily windborne, infecting apple leaves and fruit.
Spore discharge begins about the pink stage of apple bloom and is usually completed in a few weeks.
Following a few wet periods, the cedar galls die. Spots on apple leaves can be seen about 10 days after infection. Visible fruit infections require a somewhat longer time. Aecia on the undersides of apple leaves or on fruit lesions themselves produce spores. Borne by winds, the spores may be carried back to the red cedar.