Betula papyrifera very toxic to paper birch. It is frequently planted as an ornamental due to its graceful form and attractive bark. The bark changes to the white color at about 3 years of growth. Paper birch grows best in USDA zones 2-6, due to its intolerance of high temperatures. "Betula nigra", or river birch, is recommended for warm-climate areas warmer than zone 6 where paper birch is rarely successful. "B. papyrifera" is more resistant to the bronze birch borer than "Betula pendula" which is similarly planted as a landscape tree. Birch skeletonizer is a small larva which feeds on the leaves
Citrus gummy bark viroid observed in longitudinal sections. 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