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Birch dieback is a disease of birch trees that causes the branches in the crown to die off. The disease may eventually kill the tree. In an event in the Eastern United States and Canada in the 1930s and 1940s, no causal agent was found, but the wood-boring beetle, the bronze birch borer, was implicated in the severe damage and death of the tree that often followed.
The primary species affecting birch trees in North America are Profenusa thomsoni and Fenusa pumila. Areas inside the leaves are consumed by the larvae, affecting the leaves' ability to produce food. Yearly browning of birch leaves are noticed in mid July and August, but the leafminers have been feeding inside the leaf tissue since early spring.
These leaves usually fall before the normal leaves grow elsewhere on the tree. [3] There can be several witches broom in a tree. [4] Witches broom, formed by Taphrina betulina can be found on dwarf birch (Betula nana), Betula nana x pubescens, silver birch (Betula pendula), downy birch (Betula pubescens) and Betula pubescens var.glabrata. [1]
Despite this, the borers can still damage the trees if they are weakened by other means. Between about 1930 and 1950, many gray birch trees, along with paper birch and yellow birch (Betula alleghaniensis), were weakened by birch dieback disease, which allowed for the bronze birch borer to attack and kill the trees. [11]
Tar spot is a localized disease that causes mostly cosmetic symptoms and is therefore not a highly controlled disease. [3] One of the best ways to manage the pathogen is through proper sanitation techniques. [3] Because the fungus overwinters in diseased leaf debris, removing the debris in fall can help reduce the occurrence of the disease. [3]
The leaf base of silver birch is usually a right angle to the stalk, while for downy birches, it is rounded. In terms of genetic structure, the trees are quite different, but do, however, occasionally hybridize. [6] Betula pendula silver birch catkins and leaves, Childwall Woods & Fields, Merseyside
The disease gets its name from the black patches that grow on the trunks of infected trees. In a newly infected tree, branches become denuded and then die off. Eventually, the entire tree succumbs.
Because this disease is caused by multiple species within the genus Armillaria, it has an extremely broad host range. Hundreds of trees and shrubs are susceptible to root rot to varying degrees. In fact, the only two genera of tree known to be resistant to Armillaria root rot are larch and birch. Further investigation is being conducted for ...