1. Dragan Karadžić, University of Belgrade-Faculty of Forestry, , Serbia
2. Ivan Milenković, Phytophthora Research Centre, Mendel University, Zemědělská 1, 613 00 Brno, Czech Republic, Czech Republic
3. Snežana Obradović, Univesity of Belgrade Faculty of Forestry, Serbia
4. Vesna Ćurguz, University of Belgrade-Faculty of Forestry, , Serbia
The term ʺcankerʺ is broadly used for the diseases that cause the death of definite and relatively localized areas of bark on branches trunks of trees. Strictly speaking, however, repeated callusing is necessary before a lesion can be classed as a canker. Although the most cankers are of fungus origin, they can be caused by non-infective agent such as frost, sun scald or illuminating gas. Death of the bark and cambium is followed by death of underlying wood, although the causal organism may not penetrate the wood. Cankers may be either annual or perennial. The perennial cancers are usually most destructive and conspicuous.
Sometimes a disease agent kills part of cambium and adjacent bark. The cambium around the lesion produces new tissue which grows inwards to cover the dead area. With annual cankers the agent causing the disease is operative for one season only, the injured tissues than being sloughed off or grown over by single callus in the same way that a mechanical injury is healed. With perennial cankers the causal agent is active year after year. Repeatedly the new callus tissue that the host develops around the border of the lesions is killed, until the canker consist of more or less regular concentric ridges around the point of the first infection, the so called ʺconcentricʺ or ʺtarget cankerʺ (like Nectria cankerʺ). Galls and witches' brooms are common on hardwoods and conifers. Galls are globose or subglobose swellings on trees, although they usually occur on an occasional tree rather than on the majority of the trees in a stand. Galls can be non-infectious and infectious. Non-infectious galls are apparently the result of some injury or as result from external climatic or soil conditions and internal gummosis, but in which the cell walls or contents are not dissolved. The cause of the huge galls or burls so common on the trunks of conifers (for example spruce, Douglas fir, pines and other) is explained by mutation, or by a hereditary predisposition of certain trees to gall formation in response to unknown environmental factors. Infectious galls are largely caused by bacteria and to some extent by fungi, and there are infectious galls of which the causal agent is still unknown. Insect also cause a great variety of galls. In general trees with galls either on the branches or trunk, except those with many galls, seem to grow vigorously.
The most frequent parasitic fungi that cause cankers, galls and witches' brooms on forest trees are:
1. On hardwood trees
Botryosphaeria dothidea (Moug. ex Fr.) Ces. & De Not. – (Botryosphaeria Canker and Diebacks)
Cryphonectria parasitica (Murrill) Barr. – (Chestnut blight or Endothia canker of chestnut)
Dothichiza populea Sacc & Briard) Kleb. – (Dothichiza Canker of Poplar)
Inonotus obliquus (Pers. Fr.) Pilát, Inonotus nidus-pici Pilát, Inonotus hispidus (Fr.) Karst. - (Cankers and wood-destroying fungi)
Neonectria coccinea (Pers.: Fr.) Rossman & Samuels - (Beech bark disease)
Neonectria galligena (Bres.) Rossman & Samuels - (Nectria canker)
Phomopsis sp. – (Phomopsis Galls)
Taphrina carpini (Rostr.) Johanson (witches' brooms)
Valsa sordida Nitschke (Cytospora Canker of Poplar and Willow)
2. On conifers trees
Cronartium spp. – (rusty fungi)
Gremmeniella abietina (Lagerb.) Morelet – (Brunchorstia dieback)
Lachnellula willkommii (Hartig) Dennis – (Larch canker)
Melampsorella caryophyllacearum (DC.) J. Schröt. – (fir broom rust, cankers on firs)
Phomopsis lokoyae Hahn (Phomopsi Canker of Douglas Fir)
Sphaeropsis sapinea (Fr.) Dyko & Sutton (Sphaeropsis Blight of Pine and Other Conifers)
Acknowledgement: We are grateful to the projects TR37008 and TR31070, financed by Ministry of Education, Science and Technological Development, Republic of Serbia
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Датум:
01.08.2017.
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