The genus Betula consists of about 60 species of deciduous hardwood trees and shrubs native to Europe, Asia and North America. Commonly known as birches, they are most often associated with the popular white-barked types. However, other species offer distinctive bark colors and textures for the landscape. Stem canker and leaf spot diseases are a problem on some birches. Potentially damaging insect pests include aphids, Japanese beetle and leaf miner, but the most serious pest for most birches is the bronze birch borer.