Tree diseases caused by bacteria and viruses.
Bacteria, just like viruses, do not play a major role in the pathology of trees. Bacteriozy, i.e.. tree diseases caused by bacteria penetrating through injured healthy tissues, are relatively rare, however, they also have to be taken into account. Damage to plant tissues may vary. Some bacteria can break down the middle laminae between cells, which leads to structural changes in tissues. Inside bacteria, living mainly in vessels, may cause their obstruction, which leads to the withering of the branches; it happens e.g.. at willows. Trees infested with bacteria often react abnormally (hypertroficznym) tissue growth in infected areas, often visible as growths on branches, stump or roots; this is called. bacterial cancer. Bacterial crayfish can be found on poplars, horse chestnut, walnut, ash. Bacterial cancer of poplar, caused by Aplano-bacter populi (Smith), can cause the death of trees of all ages. It occurs mainly on poplars belonging to the balsam sections (Tacamahaca).
Of the virgin trees found on trees, i.e.. diseases caused by viruses, one can mention mosaic or speckled discoloration of poplar leaves, Open, elm trees, ash tree, rowan, euonymus and other trees. Curliness may also be a symptom of infection of leaves or needles by viruses.
Parasitic higher plants
A relatively common semi-parasite of deciduous trees (less often coniferous) representing the higher plants is the mistletoe (Viscum album). It occurs on a variety of deciduous trees, fir mistletoe (V. abietis Bach.) mainly on fir, and the mistletoe has scattered - (V. Iaxum Boiss.) - on a pine tree.
Mistletoe is a semi-parasite, i.e.. it extracts mineral water from the host tree, while organic compounds are produced by itself, using your own assimilation apparatus. The sometimes encountered view of the possibility of giving the host some assimilations is unlikely, for there are no proper connections between the mistletoe's and tree's ethmoid tissues.
Regular dieback of the branches above the mistletoe's growth is observed. In the tissue of the host tree below this point, the N content is lowered, P i K, while the level of Ca increases. Trees with massive crowns are dying. Mistletoe causes the greatest damage among conifers and apple trees.
In addition to depriving the tree of nutrients, mistletoe causes the formation of large swellings, the so-called. have grown mistletoe. The mucus of bursting fruit may also have a detrimental effect on tree tissues. For these reasons, then, mistletoe must be removed, although this can often be technically very difficult. Removing it also seems to be purposeful for aesthetic reasons.
The most important tree diseases are listed in the table. It is informative.
Table. Parasitic fungi found on trees in the city.