Taphrina infects newly developing leaves as the buds open in the spring but symptoms often do not develop until later in the growing season. As the infected leaves are maturing, the fungus grows within the epidermis, beneath the cuticle. When many lesions develop on a leaf they can coalesce to cause a total collapse of the foliage. When trees are severely diseased on an annual basis, growth is stunted and vigor is reduced, making trees susceptible to opportunistic pests and pathogens.