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European Canker



P_nectriacanker2

European Canker

Usually appear in

All Year


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Caused By:-     The Fungus Nectria galligena

Description

The fungus in the advance stages. This fungal species is a frequent cause of cankers in apple, pear, beech and other trees. It produces cankers in the wood of branches and trunks and severe attacks can result in the loss of a branch or the death of the trees. It is is one of the most destructive diseases of apple in Europe where it is called European Canker. The first sign of disease is usually a red/brown spot around a leaf scar, a wound damage or a small dark sunken area in the wood, which over time enlarges eventually becoming elliptical in shape in the direction of growth. The bark in this area often splits and at first sexual spores(conidia) are produced on creamy-white fruiting structures, usually soon after infection, from the mycelium in the tree wood. Later very small(0.25 mm diameter) round red fruiting body(Perithecia), looking like miniature lemons, which contains spores(ascospores) may be seen at the edges of the infection. These are the overwintering stages along with the mycelium within the wood of an infected tree. The fungi penetrates the cambium layer and underlying wood then spreads out. As the Cambium tries to regenerate to form a protective layer the fungi repeatedly kills the new callus tissue. This gives rise to cankers with concentric oval rings of dead callus tissue. The oval nature of the canker is due to the growth of the branch and therefore is in the direction of the branch. Both types of spores are released and spread by wind, rain and insects like the woolly aphids. New infections take place through open wound damage, leaf scars or frost damage. Fruit is sometimes affected, but usually do not show any symptoms until they are stored. Picture from Wikimedia Commons.
See these other Cankers Apple and Pear, Bacterial, Bleeding, Canker, Cytospora, Horse Chestnut Bleeding, Mulberry, Parsnip, Pear and Apple, Phomopsis, Poplar Bacterial, Rose Stem and Dieback, Willow Black, Sawflies.


Control

Eradication of this fungi is almost impossible as the spores are always present therefore control is best achieved by the removal of infected branches and or trees, avoiding wounds, sterilise pruning tools before pruning an uninfected tree and conduct pruning operations during dry periods when spores are less abundant. It is said that some species of trees affected by this fungus is somewhat resistant to it, probably because the bark is thicker and harder to penetrate or less likely to suffer frost damage. A winter tar or fungicide wash is recommended as well as pruning out infected areas.



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