Betula utilis to overuse of the tree for firewood. "Betula utilis" was described and named by botanist David Don in his "Prodromus Florae Nepalensis" (1825), from specimens collected by Nathaniel Wallich in Nepal in 1820. "Betula jacquemontii" (Spach), first described and named in 1841, was later found to be a variety of "B. utilis", and is now "Betula utilis" var. "jacquemontii". In its native habitat, "B. utilis" tends to form forests, growing as a shrub or tree reaching up to tall. It frequently grows among scattered conifers, with an undergrowth of shrubs that typically includes evergreen "Rhododendron". The tree depends on moisture
Citrus gummy bark viroid Citrus gummy bark viroid The citrus gummy bark viroid (abbreviated CGBVd) is a sub-species of the hop stunt viroid, and thus is a member of the genus Hostuviroid. As the name suggests, the citrus gummy bark viroid causes problems in the bark of the sweet orange tree. Scrapping the bark exposes localized spots or a line of reddish-brown, gum-impregnated tissue around the scion circumference especially visible near the bud union. The discoloration and gumming may extend above the bud union to the main branches of the sweet orange while in severe infection dark streaks of gum-impregnated tissue may also be