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Bleeding cankers are infections of the bark of trees, including horse chestnuts, by various species of Phytophthora. Infection causes cankers (bark infections) which bleed a dark or reddish- brown sticky fluid.
Bleeding canker is an infection of the bark of several trees by a number of different species of the fungus-like (Oomycete) micro-organism Phytophthora, causing the affected bark to bleed a dark sticky fluid. Cankers may be present at any time of year.
Trees commonly affected in the UK include Aesculus (horse chestnut), Tilia (lime) and Alnus (alder).
Horse chestnuts continue to be affected by Phytophthora bleeding canker at a relatively low level, but have recently been affected by a huge upsurge in cases of bleeding canker caused by a bacterium.
Holly is affected by Phytophthora ilicis, which is more commonly the cause of leaf blight but can also infect bark, causing cankers.
Alder is affected by the newly described P. alni, which has been shown to be a new species formed by the hybridisation of two other species, neither of which affects alder. This is a worrying development and spread of the disease is being monitored by Forest Research scientists.
You may see the following symptoms:
Infected smaller branches are best removed and destroyed to prevent the spread of infection.
Scrape back cankers on trunks and larger branches to remove the outer bark and reveal the extent of the infection. Exposure of the canker to dry conditions may cause it to dry out and slough off. If the cankers are small it may also be possible to remove the infections by cutting away the dead bark. However, as noted below, if infection has reached the cambium, healing is only possible from the edges of the infection. This will leave the wood exposed for many years and is likely to lead to decay.
There is no chemical control available to gardeners for control of bleeding canker.
The genus Phytophthora contains a large number of species which cause root rots, foliage blights, fruit rots and bark cankers on a wide variety of plants. These fungus-like organisms are among the most damaging plant pathogens. They spread by releasing swimming spores (zoospores) into water and may be dispersed in water or in wind-blown rain. They also produce resting spores that can be spread in soil.
The species that cause bleeding canker on trees infect through wounds and also probably through naturally-occurring cracks and lenticels (breathing pores) in the outer bark. Infections spread in the living inner bark, killing it and provoking the tree to produce a dark liquid which bleeds out onto the outer bark.
Growth of the lesion (infected area) is related to bark moisture content and in dry conditions cankers may stabilise and be sloughed off. However, if the infection reaches the cambium and kills it, the infected area can only heal by regrowth from the edges. Cankers may persist for several years, stabilising in dry conditions and then breaking out again when rainfall is high.
Bacterial cankerBracket fungiHoney fungusHorse chestnut bleeding cankerPhytopthora ramorum and P. kernoviaePhytophthora root rotWhy has my tree or shrub died?
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Witchhazel on 02/03/2015
In south wales i have found similar symptoms on several silver birch in a woodland. This does not seem to be usual in the uk though is recorded in usa. Has anyone else come across this?
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